Memory config - 768MB vs 512 MB?

Hi All,
First up thanks for any help. I have a 512 MB 400 Mhz memory module along with a 256 MB 266 Mhz memory module. Now I am trying to decide whether to put both in or just the 512 MB module in. If I put the 256 along with the 512, then my memory runs at only 266 Mhz, but if I put only the 512, then my memory runs at 400 Mhz. My question is what should I sacrifice? Should I sacrifice the Mhz and put all the 768 MB memory in, or should let the 256 Mhz go and run my system at 400 Mhz with only 512 MB? What would make my system run faster. BTW, I think the memory is Non ECC

I usually play games on my system which is a P IV 3.2, Intel 865 GBF, Raedon 9800 Pro (128 MB).

Thanks again guys
S

i agree with fishmahn... i had the same exact configuration for a few years... the 512 being higher and whatnot... (before i had much computer knowledge) i was told by a friend to take out the 256... worked alot better after... but yeah... seriously... go for another 512... u won't be disapointed