But...why? So you can see the numbers in the net graph? Your average screen refreshes at 60-70hz...that is 60 cycles per second...so basically, at 500fps, your screen isn't even showing 93% of those frames. Waste of money.
I have 3 monitors for eyefinity and play games that require more processing than CS:S? Besides, i get >300fps on max with CS:S with 1 card. I agree, 2 was overkill, and even 1 blitzes everything. But anything over 80-90fps with your lowest fps not being under 70, is quite literally all you need.