im on the verge of upgrading my desktop pc. the athlon64 is intrigueing and inexpensive if you start at the bottom of the line. my current 1gz athlon is great for 99% of what I do but its just fallen off the edge of whats needed to play games. plus it'll be interesting to make a jump into the 64bit world. abit, my favorite mobo manufacturer, makes a nice socket754 board.
ABIT KV8-MAX3 $109.99 from Fry's ATHLON64 2800 $140 seen on pricewatch, no local vendor yet RAM $unknown
everything else in my PC can stay the same. The mobos these days are awesome - 6 channel sound, Serial ATA, and gigabit ethernet.