Eh, You might have preferences for some of those things, but I would suggest looking into:
Typhoon III RO/DI system with twin DI kit, TDS meter, two extra stages for sediment and water softner. I'd also invest the extra $50 for a little computer that tells you when filters need to be changed.
A Tunze Osmolator is perhaps the best ATO on the market, and I would consider JBJ next to the best,... but if you want a fully automated system you can use the break out box on an Apex controller.
Neptune Systems Apex controllers are high end controllers that are worth the extra money and fuctionality. They offer a lot more versitility, with easy programming language and easy plug and play type controls. Best bang for your buck, and MANY modules that you can buy for it that controls different functions
Reef octopus is a great brand of skimmer - but I would look into the new POV line skimmers. They don't have a housing, so they are more efficient with less wattage.
Koralia is an ok brand of powerhead. They get the job done, but if you want the versitility of a variable speed pump to replicate the natural back and forth ocean currents, an Ecotech Vortech MP40 should definitely be on the list. Flow is very important in a reef tank.
I can't speak for proflex sumps, I used to have one, but it was the smallest one they had - a 16g. I didn't like the way I couldn't customize anything. IT was tight and compact and it only had one chamber. I'd much rather custom build or have something custom built (once you get some experience under your belt... ) Have it to where you can easily mount your probes in the sump, and all of your drip lines from any auto dosers or calcium reactors.
A Mag Drive 12 pump is a huge pump for a 75g tank. You don't really want that much water going through your sump at a time. You will want something slower - in the 750gph to the 950gph range. A Mag 9.5 will do well and I do recommend that pump still, but recently I have used Quiet One pumps and I am very satisfied. Quiet One also uses about half the electricity of a mag drive and has more forward pressure - which is great. I use a Quiet One model 4000 on my 75g with a 20g sump. Works like a charm.
You should already have a calibrated refractometer. Get one ASAP.
I'd also look into building a side cabinet for the tank, or have a custom cabinet and stand built for the tank. The cabinet would contain a three or four ten gallon tanks. One for mixing saltwater and pumping it into the tank. Another for a 10g fuge that is separate from the sump. Another is for your RO Unit to hook up to a float valve so that your ATO system constantly has a fresh supply of RO water. The fourth would just be to add extra water volume - set it up as either a Really Deep Sand Bed for nitrate->nitrogen gas conversion or you can do a separate tank for a mantis or something cool.
I'd also look into putting a large container in the garage - one of those cylindrical plastic containers - so that you can always have at least 55g of water ready to go at a moments notice. You can put a pump on it to not only mix saltwater but also push it to the display tank through a python hose. Two containers would be cool, so you could mix saltwater in one and have freshwater in the other in case of human emergencies (break in the water supply, tornado, hurricane, drought, etc.etc.)
Now add all that up on a list and you might be close to a dream tank. Of course, a 75g is not really that big. You would want to go a little bigger eventually. A 180g is plenty big, but plenty small enough not to be overwhelmed.
