I'd stick with the nVidia screamer, darn expensive though! I'd rather go with the EVGA GeForce GTX 260 896MB 448-bit
if you're going to spend that kind of money, the specs are way better, lower clocks but more stream processors and memory but I have no experience with either, yet.
I think it's time to put your 3650's on the auction block, I wouldn't spend more bucks to be able to use them. I know it must be painful but either of those above cards will singly beat them 3650s hands down. I know you want to fold and you'll knock the crap out of me with either.
I've heard from Fred_G that 8800GT's are going for $80 each now somewhere, you may want to look at getting a couple of those if the price pans out.
Oh, the GTX 260 is a big card, make sure you have room for it.
Everything that irritates us about others can lead us to an understanding of ourselves. -- Carl Jung
eVGA X58 tri-SLI, i7 930 @ 3.8GHz., Corsair 6GB Dominator, Inno3D GTX470, eVGA260
ASUS P8P67 Pro, i7 2600K @4.60 GHz, 8GB RAM, eVGA GTX 460