The P3 dualie you have now was a pretty monster rig not too long ago. But alas times, technology and apps change. And with XP Pro wanting more power you almost have to use a serious rig to run multiple apps like most of us do.
Hell...on any given day I'll have AC8.1 running along with MS Excel ( gotta make invoices ya know!), Word.......Opera Web Browser, and sometimes I'll forget that Artlantis is running...ouch!
With dual cpus I can still work in AC8 and see no slow downs.
The P4s with hyperthreading do work better than those without. We have a few - P4 2.8. Ive heard that the higher end ones- P4 3.0 or higher rock esp. if you overclock, buts that's a whole nother topic.
With the new AMD Opterions and higher end P4s still priced like gold, you can snag a pretty decent pre-built dualie now. Dells Precision workstations are great but overpriced I think. Check out www.2cpu.com
...(for sale or trade)..There's always some geekoid who's wanting the latest-greatest set up and are selling off their current rigs.
But take it from me......AC8 openGl wants a fast video card. Save your money by not buying the latest greatest P4 and buy lots 'o ram, fast video card, and decent HD.