Clock speed is not a reliable indicator of performance anymore. AMD CPUs perform much better than Intel CPUs at the same clock speed, thus only the 3GHz Intel ones can compete.

If you're looking for a upgrade, I'd stray away from S754 or Socket A. They're both outdated, especially SocketA. You're better off getting a Socket 939 motherboard with an Athlon 64 3000 or higher. That'll give you more upgrade options if needed.