Here is my opinion, from having used air stone skimmers like ages ago to now.
get your sump first if the skimmer is going inside the stand.
Measure how much space you have in regards to height.
If you make your own sump you don't have to worry about the foot print because you can customize the compartment size.
Once you know the height you need to work with aim for an internal Cone skimmer, the largest you can buy even if you plan on keeping one single damsel in the tank. Reef Octopus actually has really nice affordable cone skimmers, aim for something that is rated for 300 to 400 gallons, Eshopps makes really nice skimmers as well and there is a S300 cone for sale on Ebay right now for $469 shipped, much cheaper than many others.
Odyssea 55w UV's will work fine, you can get two 55w units for under $200 and bulbs are like $10 bucks if you buy in addition to the units on same purchase.
ATO, you are going to get opinions about Tunze but its too expensive to do the same as what Autotopoff.com sells and what they sell works, for like $50
The pump, depends of what you want to do with the pump, first decide if you want to run other equipment off the pump or if it will be strictly for return purposes. If you can go external get an external pump very easy to change if it goes bad assuming you set up the plumbing to allow for quick disconnect. If you must go internal a Mag18 or the Eheim pump mentioned are common choices.
As for reactors, just get the Bulk Reef Supply or Two little fishies reactors for carbon and GFO if you plan on using that. If you are not careful you will end up spending hundreds on common media reactors for no reason.
As for advanced reactors such as alk, cal, bio pellets and whatever else, that I dont get in to, never had them, know the brands but I dont agree with the huge price tags on them but plenty of ppl use them, you probably want to find out which are the best value for your money while still highly reliable.
Keep the two wp's and just dial them down with a regulator if dont already have one.
The fact that you have wp's and reef breeders tells me you seek the most bang for your buck which is a fine thing to do given the cost of the many other things you will end up putting in that tank.
Like I said, just my opinion with the best intentions in mind and dont want to argue with anyone about Sicce pumps versus bubble blaster and so on.
