I have never used a V5, but when you play first-person games such as half-life, 4xFSAA will absolutely kill the frame rate. I suggest you use the "single-chip" FSAA mode. (I think that's right...) You should be able to get at least 40+ full time with that setup. Try running in higher resolutions and with less FSAA.
3D Prophet II MX
SB Live! Value
running 6.49 Detonators
5209 3D Marks @ 1024x768x16
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