9600pro 128MB = 400/300 ?(DDR)
9600pro 256MB = 400/200
9600XT 128MB = 500/300 ?minimum ? a lot are 500/325
Sapphire made some 9600XT?s 256MB that were clocked 500/300 with 3.6 TSOP Samsungs -- people were getting to 340MHz overclocks with that memory but apparently they are now showing up clocked 500/250 which I believe is the standard clocking for a 256MB 9600XT.
If I could get a Sapphire 9600XT 256MB clocked 500/300 for the same price a 128MB, then the extra memory really doesn?t hurt, but if it?s 500/250 then you take a performance hit and since 256MB isn?t needed in a midrange card it?s really not worth it.