You need a modular PSU and I agree... the NeoPower 650 is very sexy
and you'll be happy with that, it's an incredible unit. The Antec 900 has 2 optional 120mm fan slots, one is one of the drive cages and the other is one the side window, I'm going out tomorrow to buy two 120mm Thermaltake Thunderblades for those two to improve my graphics card cooling even more.
Don't be so stressed, the Antec Nine Hundred is a killer case and so is the PSU you bought, I'm happy you got those two
I've got the Nine Hundred and a NeoHE 500W (The little brother of the NeoPower Blue) and I couldn't be happier.
EDIT: I might even try to get a pic tomorrow night after I'm done setting the new fans... hopefully they'll have some blue LED ones left.