I was running Abits and AMD for a while and albeit they tend be a tad faster than Intel/Asus, they tend to be more loving-care-needing as well. My last (before my dual Xeon setup here) was Asus P4P800 (any P4.800 from Asus seem to be good go), lan on it, good sound on it, lots of USB ports. It was extremely solid, overclocked or not. Anything under 3GHz hyper-threading Pentium4 is good price and you can tweak it higher, given you buy _good_ memory. Make sure it's dual bank and 400MHz rating at least. Get a good, quiet cooler, a pound of copper at least with a silent fan. Get a nice aluminium case, it's worth the money, that's the one you'll keep for longer than the rest ;-) I like atcs but there are others. Get a _very good_ power supply, otherwise your life will be hell. Enermax is not the most quiet but very solid and relatively cheap. Very quiet, very good supplies tend to be expensive. Graphics card is a whole religious war, I have ATI now but used Nvidias before, the speed/feature optimum shifts all the time. Forget PCI-X for the moment, AGP and PCI is way cheaper and stable.
Don't buy from the cheapest place, give a good dealer couple bucks extra, for that they will take stuff back and even more important, they have the stuff available.
I highly recommend Tom's hardware website to check on components.
There are coiuple good sites about PC-building from components. It's not magic and you get the best of the breed albeit you'll spend time learning stuff you may not care for.