Gifting my Bro a PC

I think I'm going to build a bare-bones gaming PC for my brother as a gift and make some upgrades to mine at the same time. Shove the old crap off mine onto his "new" one. I think the budget will be $600. I think I would be re-using from parts I have laying around (don't laugh, this is meant to be a cheap build):

21" CRT monitor
7800GT
2GB corsair PC3200 DDR (as far as I know this is still the fastest compatible RAM for my Asus A8N SLI Premium)
500w PSU


I still need to find (to migrate my 9800GT and PSU into):
Case
mobo
CPU
2gb ram
HDD


If someone wants to help me with some research on Newegg, emphasizing price over speed I'd appreciate the advice. Post any links to components here and I'll update it as I go. This thread is just to help me organize the build. Thanks.