Can i crossfire 6850 @ PCI 2.0 16x/4x? What about 6870?

[N11Ckk123472]

I currently have one MSI 6850 overclocked @ 940 core 1170 mem, stock volts.
I would like to crossfire it with another one but my motherboard only has a 4x slot.

I've looked up benchmarks and seen that gives a huge performance hit, but the benchmarks have been with high end cards. I've heard from other people that low/mid range cards will see only like a 5% performance hit.

Can I put another 6850 in and be okay? Would crossfiring a 6870 with my 6850 help compensate, or would it drop to 6850 speed?

I would like to buy a faster single GPU card, but adding another 6850 seems to be the cheaper option.

Thank you

Specs:
AMD Phenom II X4 965 Black Edition @ 3.8ghz, stock volts, Corsair h60 in push/pull
Asus M5A97 AM3+ 970 Motherboard
Wintec 4gb 1600 DDR3 Ram
MSI 6850 OC Cyclone edition with Aftermarket Gelid Icy-Vision vga cooler
Seagate Barracuda 1tb 7200RPM HDD
OCZ ModXStream 600W Modular PSU
Windows 8 Pro 64-Bit
Latest AMD 12.11 beta drivers.

 

[Maziar]

I don't recommend 16x4x for CF because the performance isn't good as dual 16x or dual 8x.So I recommend getting a mobo with dual 16x slots in order to get the maximum performance offered by your cards

 

[Phyrexiancure]

4x hold performance back past something like a 6770 or a 7750. Since you've overclocked this it'll be even more of a bottleneck. Possibly creating micro stuttering.