4870 CF or 5870

ATM I have two xfx 4870 1gb's in a crossfire config and since I'm not completely satisfied with the performance I'm getting I was wondering if it would be worth it to upgrade to a single 5870. I'm confused about the performance of a 5870 compared to my current rig because there are no benchmarks out there that i can find comparing these two setups. I have seen benchmarks of the 5870 using the crysis benchmark tool getting an fps avg of 35 running DX10 very high settings at 1920x1200 res. I did the same benchmark with my config and got and avg fps of 19. Normally this would just say duh go upgrade to the 5870 because the performance increase is pretty significant not to mention getting DX11 support, but I'v also read of people getting benchmarks comparable to the 5870 with my config. I'm just not sure if these are legit or not. If they are is there something wrong with my system?

So is it worth it to upgrade or should I just stay with what I have for now, or is there an issue somewhere?

And in case you think my other system specs have something to do with it here they are

CPU: Core i7 920 @ stock 2.66Ghz (btw all the other benchmarks I looked at are using this with OC's)
Motherboard: MSI X58 Pro-E
Ram: 12gb's A-Data DDR3 1600mhz
HDD: 2 1tb 7200rpm
power supply: 1000watt

Aa single 5870 would not be faster, about the same.

(Sometimes even slower)

That setup seems fast, I would stay with it.

But if you're pockets resmble a coal mine, then a 5970 WOULD be a upgrade.

(Maybe you could do a mild OC to the range of about 3.66ghz?)

Performance wise it is not worth it! As is you have a great system, consider upgrading on the next series HD6xxx. Maybe by then DX11 games will be rolling out.