GPU Advice

I've got 2 rigs that have weak GPUs- one is mine and one is my brother's.

I've got a GT 640 from EVGA which is weak. I'm looking at EVGA's GTX 660 FTW, and I'm going to wait for the 700 series for either the 760 or to buy a 660ti at a lower price. MSI and ASUS are also brands I am looking into. My question is- when I upgrade to a 660, 760, 660ti or whatever; what brand do I buy (and why), and should I use my 640 as a dedicated PhysX card, or let it rot in some old box?

My brother's rig is quite similar to mine (on my profile) but he's got an i5-3570k, 8gb of RAM and a Sapphire 7770 HD GHz Ed. I am considering two options for him- 660/660ti/760 or getting another 7770 and Running CrossFireX with them.

I am open to AMD options on his rig but I appreciate the CUDA cores that I use on mine. I'd like to know the best budget-minded upgrade to ready us for newer games on medium high to high settings. Any and all help is greatly appreciated.

For you just get a gtx 660 or 660ti brands asus, msi, evga are probably the best. For your r brother sell the 7770 and get a 7870 you can do crossfire but not all games use it effectively is why i say get a 7870 over 7770's 

I agree with raging. 1 7870 will be more usable than 2 7770