Not quite sure if this is applicable to the 9600, but many of the lower-end cards with 26mb ram runs slower than their 128mb counterparts...
This is because slower (and cheaper) ram is used, and this holds back the card from realising it's potential....
Therefor, I'd suggest you check very carefully with the shop selling the 9600 256mb EZ to find out what speeds the core run at, and what the speed/who the maker of the ram is...