Are those the tank dimensions you want to stick with or is that what was in stock?
I only ask as GlassCages (just one of a couple custom builders) comes in close in price for tank/stand/sump combo of similar but not exact dimensions.
(Also not dissing planet as they’re an excellent brand)
As for list, that list is pretty spot on for a basic set up.
Things I personally would change, but there will be varying opinions.
I’d change the lighting. It’s going to cost more but I’d go with something like ReefBreeders or Reefi Unos or even Quanta Atlas. All three are high quality lights but not sure of the “punch” of the Quanta or ReefBreeders for a 30” deep tank. Reefi shouldn’t be a problem for the depth as I’ve heard they’re par monsters you may just need to go 2 wide for a 30inch width to get enough light to the bottom of the tank for coral. Lighting for coral unfortunately is not inexpensive. There are cheap options that work it’s the tank dimensions that are driving the cost up some.
One thing to consider with lighting is your mounting options. That wide of a tank you’ll likely want to mount the lights from the ceiling unless you have a separate mounting system.
I would look for a used skimmer. Just make sure the skimmer size can handle the tank size. You’ll likely save some money here.
Hydros - an excellent system. I use Apex but have been looking at setting up a hydros for some of my other tanks. There seems to be semi-regular sales (10-20% off) online. My LFS also honors these sales usually too. I’m not familiar with their salinity kit so can’t comment there.
Going off hydros, it’s included in your list but definitely an ATO. This helps maintaining stability.
As mentioned RODI. My opinion, an RODI is an RODI so brand doesn’t really matter here just how big of system you want (gallons of water produced per day). Getting an RODI will also save you on buying premixed water.
With that also said, going with an RODI you will need to buy salt. I use Instant Ocean or Reef Crystals (whichever is cheapest) but there’s plenty of other great brands out there as well that people use.
Rock…I’m a live rock person but it’s pricey. You can always start with mostly dry and add some live rock to get that additional bacteria and other benefits. With that also said, if you don’t mind “white” rock, you can get Marco rock or similar dry rock for about $3.00/lb - (25lbs for $66 at KP Aquatics) -
Dry Rock - Free shipping.
As for sand, bagged live sand is great, but again you can get “real” live sand for a bit more - 100lbs for $399. You can choose a smaller amount and go with dry sand and use the live sand to seed it. Dry sand again is generally a bit cheaper. Also 100lbs of sand seems kinda low for a 280 gallon tank. I’d push closer to 1lb per gallon.
As mentioned I’d go with multiple heaters, I’d personally do 2 x 300watt. However I don’t see a heater controller (other than hydros). I’ve personally seen heaters destroy a tank by malfunctioning so I’d get a separate temperature controller (Inkbird is popular but I’ve seen them fail but Ranco is another popular brand (also used for commercial applications).
Sicce is a great brand for return pump. I personally run cheap Jebao pumps, but it’s all personal preference.
I don’t see any powerheads/wavemakers on the list. You’ll definitely want at least a couple. Again I run cheap Jebaos with not many issues. There are multiple other brands as well (AI, Vortech, Neptune, etc) that are high end brands with the high end price tag that have a following as well. You also can’t go wrong with Tunze. A fantastic brand that’s been around for decades with excellent customer support.
As you venture into corals you’ll want to integrate dosing additives.
Also test kits. Hannah is a great brand with digital read outs but I personally use Salifert (non-digital) and have never had an issue. That said, Hydros will be having the Hydros Maven coming out soon which does automatic testing.