Dennis, are you looking to go AMD or Intel?
For $150-200 the Intel route wouldn't buy you as much as going the AMD route.
For the AMD motherboard I'd highly suggest the nForce2 chipset, that thing has some nice memory speeds (very fast!) not to mention if you ever blow out your seperate graphics card you got a backup integrated graphics card(equivalent to Geforce 4 MX graphics).
So I'd suggest the Epox 8RDA3+.
EPoX info page:
click here
Pricegrabber page:
click here
They are currently going for around $95 on pricegrabber. It comes with RAID, Firewire, USB2, the works.
For the processor, you can't go wrong with an AMD Athlon XP 2500+, currently going for around $105 on Pricegrabber retail/boxed.
Pricegrabber Link
Hope that helps.