On the other hand, you'd see a nice speed boost if you switched over to Athlon 64. Just be sure to get a motherboard with an AGP/PCI lock. I'd shoot for 2.4ghz or more.
3ghz is pretty common with 2.4C's. Some people even pull 4ghz+ out of the newer 775 chips. You can't compare an Intel chip to an AMD one based on clock speed alone though, that's why AMD rates their CPUs with 2500+ etc. Even though your cpu may be operating at 2.2ghz or "3200+", gaming...