I wouldn't be so sure..
Athlon XP's are cool I grant ye... only because I have 2500+ Barton and it's brill lol.
If you were after a replacement I mean even though the Semperons have been given bad press... 2600+ is very good. Or even go for AMD Athlon 64bit which are coming down in price.
Plus also those new AMD chips are for Laptops hehe... not the best chips for power due to the fact they are built to preserve battery life.