Money is not a issue for me. Now that you mention it, I do like to play Team Fortress and I see that it is available in Steam.
My system is a x86_64 AMD Phenom(tm) II X3 705e Processor AuthenticAMD. I like how quit my systems is(low heat) and I do not want to upgrade it. It has a PCI Express 2.0 slot for gpu. How high could I go up the Nvidia line before the rest of my system would be the bottle neck? 660 or 670?