Peter, you mentioned a list of things to have on hand that I posted in nahham's 19,000 gallon reef build thread. Here is a somewhat updated version that would apply to you. I thought I should post it in this thread to keep everything in one thread. It's confusing enough stirring and sifting through this epic thread, let alone opening another can of tubeworms with other build threads.
Before I get to the list, here is an overview of how an aquarium of your size compares to a typical hobbyist tank, or nahham's larger open system on the sea for that matter. You have a very large investment that warrants all the fail-safes you can muster. Even though the scale of your project is much smaller than that of nahham, the scope is much larger as you are running a closed system with more sensitive organisms.
You have so many fail safes and redundant equipment that it would be remiss to include a second opinion aquarium monitor/controller in your arsenal. I know little about it, but the new Vertex controller with touch screen technology looks interesting. I don't think it's on the market yet, but I'm sure you can sweet talk them into a bata test version with the captive audience you have here. I assume Profilux is their main competitor so you could acquire one of these units as your secondary/backup controller. having a second opinion is great. Both units can't be right and even if you don't know which one is more accurate, you can establish a line of precision. Even a broken watch has 100% precision twice a day. The controller may not hit the target dead on centre every time even when properly calibrated, but it will at least hit the same spot repeatedly.
The other approach would be to buy two identical controllers so you are truly comparing sea apples to sea apples. This will offer you a spare parts source for your primary controller. Use only one controller to govern the functionality of the devices you want to control. It will become too confusing if you try to spread the workload. An alternative plan would be to start off with the best controller on the market and when a better one comes along in a year or two, upgrade and keep the old one as a second opinion machine. Part of the challenge will be keeping the probes and modules clean and organized, but it looks like you have experience with this from the audio video realm.
The liquid test kits by Lamotte, Hach, Merck, Salifert, Elos, and SeaChem are of good quality. Sometimes it is better to pick and choose individual tests from each company for ease of use and accuracy. As with the controller, a second opinion is vital as reagents can get contaminated or old and human error is unavoidable ("did is say add 5 drops or 5 ml, better add more just to be on the safe side?")
Here is the amended list originally posted for nahham...
1) Digital PH controller for calcium reactor body to govern Co2 dosing.
2) Digital PH controller for system water to override Co2 dosing and or dose kalkwasser and sodium bicabonate.
3) Digital dissolved oxygen meter. You can move it around, but it should get homogenous readings throughout the water column. You will however get lower readings in slow flow reactors and deep sand beds. Order extra probes as they don't last forever and cannot be calibrated.
4) Digital salinity meter.
5) Refractometer and glass hydrometer for double checking salinity.
6) Liquid ammonia test kit.
7) Liquid chlorine test kit for bleaching fishroom tanks.
8) Liquid nitrite test kit.
9) Liquid nitrate test kit (premium low range).
10) Liquid calcium test kit (premium brand).
11) Liquid magnesium test kit (premium brand).
12) Liquid carbonate hardness test kit (premium brand).
13) Digital dual TDS meter for adding pure freshwater. One for the water entering the deionizer and one measuring the water exiting. It's also nice have a hand held TDS meter to know what the municipal water source is like as it shifts seasonally in most areas.
14) Digital redox/ORP controller
15) Digital phosphate photometer (Milwaukee or Hanna).
16) Liquid phosphate test kit (low range Merck).
17) Liquid iodine test kit (premium brand).
18) Liquid strontium test kit (premium brand).
19) Liquid silicate test kit (premium brand).
20) Liquid copper test kit (free copper & total copper).
21) Quantum/PAR meter.
22) Scientific analog thermometer to calibrate digital meters.
23) Titanium ground probes.
At some point it time you should also start stocking up on chemicals to correct the parameters you are testing such as...
1) Hydrochloric acid (cleaning & lowering PH)
2) Calcium hydroxide (raising & maintaining calcium & PH)
3) Calcium chloride (raising calcium quickly)
4) Sodium carbonate (raising carbonate hardness & PH)
5) Sodium bicarbonate (raising carbonate hardness & lowering PH)
6) Peroxide (raising dissolved oxygen & redox as well as disinfecting)
7) Dry salt mix (raising salinity)
8) Sodium hypochlorite (pool/household bleach for sterilizing filters, equipment and holding tanks)
9) Sodium thiosulphate (neutralizing sodium hypochlorite/dechlorinating). Buy Seachem Prime as it also detoxifies ammonia and nitrite. Have lts on hand for emergencies.
10) Potassium permanganate (disinfecting equipment corals & fish, as well as neutralizing medications)
11) Lugols iodine (disinfecting corals & fish)
12) Formalin (treating fish parasites)
13) Malachite green (treating fish parasites)
14) Nitrofurazone (wide spectrum antibiotic)
15) Neomycin (wide spectrum antibiotic)
16) Isoniazid & rifampin (fish TB treatment)
17) Quinacrine hydrochloride (protozoan/cryptocaryon ich treatment)
18) Metronidazole (protozoacide & antibiotic)
19) Chelated or ionic copper (Mardel Coppersafe or Seachem cupramine)
20) Methylene blue (aids to clear gills of parasites in bath)
21) Piperazine & Dylox & praziquantel (dewormers)
22) Rubber gloves, disposable surgical gloves, droppers, scientific glassware, tweezers, grabbers, nets, flashlights,
23) Parasite eating doctor fish and cleaner shrimp for the acclimation tanks.
24) Flat worm medication. (Salifert Flatworm exit/Dylox).
25) Red bug medication (Interceptor/Dylox).
26) Iron and manganese based macro algae supplement.
27) Activated carbon.
28) Granular phosphate remover.
29) Fragging tools, glues, and plugs, rubber bands, cable ties and tape.
30) Floating clear acrylic viewing box for looking at the tank from the top down.
31) Acrylic buffer and polishing kits.
32) Whiteboard, notebook & labels for fishroom tanks.
33) Fish food, auto feeders, brine shrimp eggs and hatcheries, phytoplankton culture device, rotifer tanks etc.
34) Microscope or magnifying glass.
35) Algae removing sticks, single edge razor blades magnets & scrapers.
36) Gravel cleaning hose and gravel separator. Siphon hoses, strainers, water scoops, utility pumps, buckets, heaters and sieves.
37) Fish bags rubber bands and insulated styrofoam shipping boxes.
38) Feeding tubes and syringes.
39) Turkey basters and powerheads mounted on poles to blast detritus from the rocks.
40) Portable diatom filter.
41) Pest traps for worms and parasites.
42) Fish traps for fish that become pests or need to be removed for treatment.
43) Seachem ammonia alert badges for the fishroom tanks.
44) Ammonium chloride & sodium nitrite for cycling tanks.
45) Bacterial culture for cycling tanks.
46) Strontium for maintaing NSW levels.
47) A safe place to store all this junk, especially the next item.
48) Vodka and lots of it.
Anyone care to add anything I may have missed?
My wife is Polish so I will be in the Baltic neighbourhood soon. I'm hoping to go to Hel this time. Everyone keeps telling me to go 
