Wondering about buying a 6950

[burningoat]

i currently own a 5770HD XFX series and i can buy another one for 130$ and xfire them
but what is the performance difference if i just got one 6950 and had the dual bios switch to make it a 6970

and also wanted to know is there a performance difference when my 2 PCIe ports are different speeds (one running is 16x and if both are running -xfire-they run at 8x instead of 16)
just something i never really known or got a straight answer for

system specs are
mobo-gigabyte 890gpa-ud3h
psu-thermaltake 750w tough power
ram-patriot G-ram @1600
cpu-amd phenom 2 x6 1100t (stock clocked)
gfx-amd 5770HD xfx series (stock clock)
case-thermaltake V9 black edition

i added my case there cause i know this card is a lot bigger then my current 5770

thank you for any help
burningoat

 

[rolli59]

I personally would go for the HD6950. X8 X8 CF takes no noticeable performance penalty over X16 X16

 

[wa1]

^+1

 

[burningoat]

Best answer selected by burningoat.