My recommendation is to stay away from AMD. They are basically a clone of the Intel which means they are not as good. They boast the same or higher clock rates but do not have the on board cache memory of the Intel hence slower running applications. Now, if you were to buy the new 64 bit AMD, they are screamers. All reports are they outperform the Itanium 64 bit from Intel but stand by Intel won't put up with that for long.
Stay away from PC's with Celeron chips also. Some advertise Intel inside when it has a Intel Celeron. Again this has much lower on board cache and slower application performance. Get one the says it has a Pentium 4 at least.
Just my opinion and I use, spec, quote, deliver, design, compare, and deliver real time systems with them.