Looks like everything is coming together nicely. Congrats on getting the C-of-O so quickly and of course the big upcoming move! No more condo
It's funny because when I saw the photo of your sump outside the closet, it seemed to big to make it in but I figured there must be a way to shoe-horn it in there. But I agree with you, it all worked out the way it should, now you can have a window to show off that amazing RE creation.
Definitely check out Spectrapure for your RO/DI, ATO, and water change needs. They are local, in Tempe right off the 101. I have their 180gpd Maxcap unit which I would definitely recommend, and it is very reasonably priced. If you ever need replacement parts you can drop in and they'll take care of you. Their Litermeter system works great for automatic water changes and ATO, and doesn't even need a controller. They won't set it up for you, but I'm certain that would be child's play for your plumber based on the other work he has done.
And there is a place in Tempe that sells Norwesco water storage tanks in all shapes and sizes, I'm actually heading there tomorrow morning myself to pick up a couple 50g or 105g tanks to set up a saltwater mixing station. I'm sure your plumber knows of them. You should be able to set up a very good ATO and water change system for less than a 1/10th of that ridiculous quote. With a little effort, you can even set up a single continuous water change & ATO system using two dosing pumps and diluted saltwater, where say x gallons a day of tank water is removed and replaced with new salt water that is diluted with extra RO/DO to make up for evaporative losses.
You will certainly want a controller for operation of other tank equipment, and for data logging and monitoring everything when you're not around. The Neptune Apex and GHL Profilux are the best. I went with the latter as the price had dropped dramatically with the favorable exchange rate, and I was already familiar with the software and programming from my old rig. It's a bit cumbersome to set up, but it is very robust and reliable once it's running, a typical German engineered product. And the support is great, they will help you with any issues that arise. You can get the Ultimate Set with remote Touchscreen and nearly all the needed accessories for about $1,000 now, I think, which is a
smoking deal - much less than the individual components sell for. You're welcome to come check mine out if you wish.
I'm sure the Apex is great too, and it definitely has more modern and user friendly software. At least when I was looking at it, there were extra pieces that one had to buy in addition to the basic kits and it was a bunch of individual components that were wired together, versus the Profilux which has a primary base station and a bus which daisy-chains the various accessories.