XFX 7900GT, maybe capped with this system

I know i know...You guys are right that you are tired of reading posts of people asking the same all over again, but it stumbles me, if this card i just aquired recently in change of my previous 7800gs is somewhat capped or not in this system.

Athlon 64 3500 at 2.5 ghz with 1 gb (2x512 ddr)

I score:

23500 in 3dmark 2001
17500 in 3dmark 2003
8600 in 3dmark 2005
4300 in 3dmark 2006


I would like to know if my system is holding back the 7900 gt card (overclocked from factory), but ONLY at 1024x768, or 1280x1024 maximum, with no kind of antialiasing on.

Last but not the least, could someone give me a opinion on what is best : 2x1024 or 4x512?

Lots of thanks in advance!

Holding by much, at that resolution?

About the ram, my doubt goes to the system stability, considering that i have major overclock on this cpu, from 2.2 ghz to 2.5 ghz via fsb..

I must make the right decision in order not to waste money lousely!
What do you think?

Hmm, seems logical.
At the moment i have 2x512 which i would like to continue to use. Will one single stick of 1024 screw my Dual DDR setting?
If so, will 2x1024 in add with the existing 2x512 work correctly in dual ddr?
Im sorry that i am escaping a little from the mainpoint of the thread, which is Graphic cards. Not discarding the previous comments, i still would like to know the opinion about the 7900GT in this type of setting.