Upgraded Hardware/Playback Engine Issues

[WeaselFlix]

I just installed a new motherboard/Intel Core 2 Quad Processor 2.5 GHz from a Pentium 4 single processor. I never really had much issue with playback/tracking/latency problems on the previous setup and now I am receiving a playback error stating I should adjust my buffer size in the playback engine settings. I've experimented with several setups including changing the number of RTAS Processors, Playback and H/W Buffer size and adjusted the CPU Usage limits. PT's recognizes all 4 processors. It seems odd that I'm experiencing these problems since I should have GAINED speed and performance from the upgrade. What am I missing? Are there optimal settings for the Playback Engine and are there settings I've failed to tweak since the hardware install? The old setup only bogged down when I was mixing with quite a few RTAS plugs running. Now it acts up in a new session with 1 or 2 tracks. I'm at a loss.

Thanks in advance for any tips.

~P

Intel Core 2 Quad 2.5GHz
4 GB RAM
Window XP Service Pack 2 (Spectral Optimized Version)
Pro Tools LE 7.1
MBox 1
KRK Rokit 8 Reference Monitors
MotorMix 8 Channel Control Surface