Very nice llama .... I have exactly the same card ... but running on a quad.
download
http://www.cpuid.com/pcwizard.php
run it and come back with this info
Mainboard : EVGA 122-CK-NF68
Chipset : nVidia nForce 680i SLI SPP
Processor : Intel Core 2 Extreme QX6700 @ 2666 MHz
Physical Memory : 4096 MB (4 x 1024 DDR2-SDRAM )
Windows Performance Index : 5.6
(I should know better at my age!)
VHG
If you look you'll see danny is wanting to change out what was (and still is) a reasonably good card ... so I think we are talking gamer here in that case the extra 256 will make a big difference ...
buy yourself a copy of BioShock and see!
Where does your info that more that 256Mb has no effect come from?
certainly not any mainstream PC mag, journal or forum I've seen in the last 8 months
Perhaps you should pick up the telling bone ... and tell your tekkie? friends that electrickery is now used in the latest counting boxes