The really cool thing about dual boards is that you can assign application to specific Processors. Also, if the application you are using is Dual processor enabled, you can really see results.
Adobe Premier is one that is like that. ONe of my systems is a dual 1.26 P3t (512k L2) and I can rip though videos in no time. My 2.8 HTp4 takes 3 to 4x longer.
I love Dual machines, but they are really for special use, not gaming or surfing. Video editing, rendering, things like that is where you will see the benifit. And Only use win2kPro for your box. XP is still working out Dual processor bugs...