The semperon CPU started life as a modified Barton core chip that has reduced cache and a high clock multiplier. The core speed of the semperon is lower than the barton core BUT it has the 333mhx bus speed. If it`s one of the newer semperons ( socket 754 ) then it has a 64 bit instruction layer effectively giving it full 64bit processing. The semperon processor is a very powerful processor as are ALL todays processors. Above all else the computer`s front side bus along with memory capacity is probably the most important thing for you to consider!
I have built computers for several of the local guys that use them as studio equipment and the most important things for them are as much ram as possible, a decent interface for your recording and fast storage capacity.
The only time the processor becomes an issue is if you intend to use many soft synths at the same time . In that case an Intel P4 6** series chip would be better (64 bit instruction layer) or an AMD athlon FX series chip (single core 64bit) . You may even look at the dual core processors by Intel and AMD, but the semperon will be perfectly adequate for what you want.
If you have cash to burn and you have the SATA connectors on your mainboard go for for a pair of 74g weston digital raptors in a stripe array for performance. They are 10,000 rpm hard drives and are the fastest drives available for desktop computers.
