As always in computers, it depends on your budget and interests.
If you're on a budget, getting a A7N8X and a 2500+ Barton should be fine, and you can always overclock a lot.
If you've got some more money, I'd advise you to get a P4C on P4P800 - something like the 2.4C or 2.6C. They are the rough equivalents to the 2800 and 3000 from AMD, because of HT and 800Mhz FSB.
If you're aiming for high end, I'd suggest looking at the 3.0C P4 on a good-quality motherboard. I'd only recommend the 3.2Ghz if you really had lots of money...
<font color=red><b>M</b></font color=red>ephistopheles