I do use HPS lights. i have 2 400watters. They do put off some heat but they have air cooled hoods and it's under control. The heat is actually very welcome this time of year.

I say you'll be good with that kit you linked to. The 250w HPS will do you just fine and it really won't throw too much heat, nothing a good exchange of air can't handle. and 78-83 is not bad at all. I've seen some rooms that get over 100 and still do "OK". 65-85 is a pretty acceptable range, 72 is ideal.

I'd say if you have 2 of your PC fans suckin' air out the top and a passive intake on the bottom you'll be pretty good (no promises though, do a dry run before you put plants in there.) keep an oscillating fan in the cab and you should have plenty of air moving.

I've never done NFT, but it looks like that kit will make it pretty easy. And don't worry about anti-detection foil. 1 250w light won't be putting out that much heat.

keep us posted!
Skeet.