Here's my take...
Unless you're gonna overclock it, don't spend extra on RAM. Even if overclocking, you can still get good clocks on the A64 with DDR2 667. eWiz had (off and on) 2GB of DDR2 667 for around $125 or so. Alternately get just one gig.
If you do want to overclock, then get a different motherboard. If you want to stick with the mATX form factor, the Abit NF-M2 nView (not the NF-M2S) is a good choice, with the Biostar Tforce6100-AM2 as runner up.
The combo that jpeyton listed seems a nice one. Board is decent enough for a cheap overclocker and the CPU should run nice and cool.
I vote for this PSU. $32 plus shipping, 300W. Yes, only a mere 300W!!! However, it may be better quality (Fortron FSP model instead of ATX model) and it is 80+ efficient (supposedly). It has enough power for such a modest machine.
Case... get whatever tickles your fancy unless you want specific features such as smaller, larger, quieter, clear side, colors, etc.
Video card choice is fine for either 7600GT or X1950Pro, depending on if you want to spend the extra $65 or not (eVGA 7600GT $90AR).