Quick Sapphire 4870 Crossfire question

Hi everyone, it's been a while since i've visited MG & I thought i'd celabrate my return with a foolish purchase & it's effect on my system.

So basically I have owned & enjoyed a ATI Sapphire HD 4870 1GB for about 2 years now running with a 19" Hannspree Xm @ 1440x900 (I know tiny these days), recently though it decided to not let me play a game on max settings without some nice lag ruining my FPS experience. So I took a look around for another 4870 1GB to Crossfire with mine to beef it up a bit until I can venture into the 6xxx series, looks as though very few places sell 4870's anymore so I took a look on eBay & turns out they sell for roughly £60-£70 which is not too great for used GPU's imo, but after loosing so many I managed to win myself a Sapphire Toxic 4870 512mb. I didn't see the 512mb part until after i'd bid &... won, so here's my question.

What can I expect to gain or not from a Sapphire 4870 1GB (GPU Clock: 800Mhz, Mem Clock: 1000Mhz) & a Sapphire Toxic 4870 512mb? Will I be selling it again on eBay hoping for a new year bargain hunter :-D

You might want a little more detail on the system, I forget if this is in my sig :-D
ASUS M4A78-E (CF X1 PCI-E 16X, X2 PCI-E 8X)
4GB 2X2GB Sticks Corsair XMS DDR2 800Mhz (don't ask lol)
AMD Phenom II 940 BE @ 3.0Ghz (stock)
Low temps, pleanty of power to go around.

:major2-Bit-Geek:major

 

Just thought i'd add a few details to this thread:

I'm still no good with links :-D

Motherboard: http://www.newegg.com/Product/Product.aspx?Item=N82E16813131368
Couldn't find much on it, must be getting old :confused

Current GPU: http://www.sapphiretech.com/presentation/product/?leg=&psn=000101&pid=179

New GPU to Crossfire with current: http://www.sapphiretech.com/presentation/product/?leg=&psn=000101&pid=182

Hope that helps, I google'd all night to see if I could find anybody who's managed to CF them & what happened, but I found nothing on an 8X mobo :confused

:major2-Bit-Geek:major