They're all basically the same,
That's no where near true. You get what you pay for. Membranes differ vastly in their waste water to produced water ratio, how many GPD can be produced. Pre and post filters differ vastly in quality and life. Automatation that can be applied to the unit. Why would you skimp on the most important aspect of running a reef tank - that being clean water that you have 100% confidence in?
As for flchevygrls questions:
The BRS water saver (any "water saver" for that matter) is going to have two RO membranes - the waste from one is put pack into #2 to give it a 2nd pass. A simplified way to think of this: Instead of throwing away 2 waters for every 1 water produced - you'll now produce 1 waste water for every 1 water produced.
The bigger benefit to double RO membranes is the amount of water you can produce in a given time period rather than saving water. Water is pretty cheap and the amounts we are producing (and throwing away) hardly put a dent in our wallets. Even if your making 100 gallons of clean water - your throwing away ~400 gallons in a single RO membrane unit. Most water billing is occurring for every 1000 gallons so you wont notice a big difference in price between 500 total gallons used versus 300 gallons used in a double RO membrane unit. Double RO units usually increase the amount of water you can produce in an hour. instead of 1/2 gallon per hour - you might get upwards of 1 gallon per hour.
Where your money is better spent is in quality pre-filters. The whole chloramine block thing is a myth. There's no difference in the quality or construction of a chloramine carbon block from a high quality carbon block. Marketing guys stamp the carbon blocks as Chloramine blocks and add an extra 5 bucks to the cost of the filter.
Randy Holmes Farley covers what a carbon block does when it comes to chloramines:
http://www.reefkeeping.com/issues/2003-11/rhf/feature/
I always buy my filters from spectrapure. They have a proven track record and have high quality all the time.
Pre-filter sediment:
http://spectrapure.com/FILTERS-MEMB...ron-Pleated-Sediment-Filter-Cartridge-10-inch
pre-filter carbon (two of them):
http://spectrapure.com/FILTERS-MEMB...RIDGES/0.5-Micron-Carbon-Block-Filter-10-inch
I dont think I would trust the filters packaged with the BRS unit for more than 100 gallons of produced water. You want to buy the smallest micron rating you can to ensure your not letting ions through tot he membrane.
I replace my pre-filters every 6 months and I produce around 100 gallons a month in clean water (that's about 5000 gallons of total water going through the RODI units I have). I replace the post filters (DI and Silica buster resins) when my TDS shows anything but zero on the output.
I personally run two of these units:
http://spectrapure.com/RO-RODI/RODI-SYSTEMS/MaxCap-1-1-Ultra-High-Efficiency-100-GPD-RO-DI-System
I have modified them to include an extra canister so I can run two carbon blocks instead of the normal one (I moved the sediment filter over to the extra canister).
I run two because of the layout of my house and the tanks I have. They are so over the top in price because they are completely automated and have redundancies to increase the life of the membrane. Autoflush after every 40 gallons or so, turn on and off automatically based on float sensors, adjustable pressure across the membrane.
