Quad Pentium II 450 Zeon w/ 2MB Cache lo

I have a Dell 6300 server that was running with a dual Pentium II 450 Zeon w/512K cache and 512MB of ram. I have since upgraded the processors to quad 450 Zeon w/ 2MB cache and 1.5GB or ram. There is no real change in the speed. I have tweaked the registry to recognize the additional cache but it really didn’t help. I am running NT 4.0 pushing about 20 users on this box. Any help would be great, thanks.