[H] how to compare

[Winterlight]

I want to replace my two ATI 5750 cards Crossfire with a single 
Nividia card that is capable of driving three large monitors plus the 
HDMI. Gaming is not an issue as long as I keep the performance I have now.

So what is the best way to compare...Core clock? So if my 5750 cards 
run at 650Mhz times two...can I say a comparable card with be a GTX 
650 which runs at 1058Mhz  core clock. Does that make any kind of sense?

What are the best, most reliable manufactures for Nvidia video cards? 
right now I am focusing on EVGA