Alright Ray, I've looked at your stuff.. Here are my thoughts
PROCESSOR: Go with the 939 not the 754 slot.
Why go with a 64bit processor? When you're running a 32bit OS (Windows XP) and 32bit applications, the performance gain is like 5% for a large increase in price until OS's go 64bit.
Some of this spiel below comes from what I learned in a comp. architecture class, at the time I believe we were dealing with the Opteron core and as such some numbers may be out of date.
With a 64 bit processor you can in theory have more than
twice as many registers on board (might now be quadruple). Along with doubling the general purpose registers it has an additional eight dedicated 64 bit GPR's and eight additional SSE2 registers. You get
true 64 bit memory addressing, no more slow paging scheme Physical Address Extensions that come with 32bit architecture after the 4gig limit is met. AMD uses a 64 bit flat addressing scheme that can hold 256 terabytes of addresses without the need for paging. It has more than twice as many SIMD (single instruction multiple data) SSE2 addresses than a 32 bit chip. The ALU is faster with newer algorithms and much larger registers, floating point calculations (the hardest/slowest thing for a chip to do) are faster and can be
more accurate. Better branch prediction and more effecient "hyperthreading" technology then Pentiums allow AMD's to perform faster then higher clockrate (ghz/mhz) Pentium 4's.
You are correct in the assumption that 32 bit OS and 32 bit applications are still only going to use the eight registers they used to have on a 32 bit machine. However, they could be recompiled in order to take advantage of the new architecture. Even without this added benefit of older applications running faster wouldn't you rather have a system which is ready for the future? If I were spending the money
today I would buy a 64 bit processor and know for a fact that in a years time it will be much more current then any of the 32 bit processors around..