I have a old machine. It is a p4 3.0 northwood with a ATI Radeon X850XT PE AGP, WinXP and 1.5GBs ram. I have been looking at various cards and at first looked at the sapphire HD3850. Later realizing that my cpu would not handle it! I bought a 2600Pro when they first came out and it slowed my pc. So I narrowed my choices to X1950 Pro, 7600GS or 7800GS. I would like to be able to get UT3, MW, MW2 L4D, and L4D2 on high settings if possible. For anyone that might say get a new machine. I'm currently saving. It's gonna take atleast two years.
Any thing less than the HD4650 will leave you with the same disappointment as the 2600pro. Bottle necking does not harm computers it only means that you get fever fps with the same GPU than the guy with a faster CPU but you will still see improvement over a lower tier GPU on your system.