| Wow, I can't believe I've missed two pages of this project already. Looks like you have a lot of work ahead of you. I'll toss in my $.02 on the chiller. It sounds like you're considering putting it in the stand? I'd have to strongly reccomend against it. A chiller is a heat pump, and generates significant ammounts of heat. It requires good circulation of cool (room temperature) air to be effective. It will heat the air in the stand very quickly and cease to be very effective.
I only have one return, and so have my chiller and UV plumbed inline with my return, but I'm thinking in your situation, you'll want the chiller on one side and the UV on the other, or one return will be considerably more restricted than the other. A pair of ball valves could help even it out (you"ll probably want them anyway, just to tune the flow), but I thik you'll be better off with one device on each return.
__________________   | 
