upgrade advise 2.2 to 2.8Ghz worth it on p4s533.

I have a p4s533 with a 2.2 ghz processor running PC2700 memory.
Assuming I replaced my memory with 2 GB of PC3200 and upgraded to a 2.8
Ghz processor at a bus speed at 533, would it be worth the money (for
games primarily)? My video card is an NVIDIA 6600 GT.

Or would it be more cost effective just to keep my PC2700 memory and
try to find a 2.8 Ghz processor with a 400Mhz front side bus?

thanks for any help!

-Doug