doom 3 has made me do it the 1.4ghz geforce2 machine dont like it too much

have got the following to swap from the old one....

few hard drives (180gb total)
sony dvd burner
tower case
monitor
keyboard
mouse
sblaster 5.1 with bass bin and surround speakers
wireless lan pci card

so i figure i need (inc min spec)

motherboard (christ knows about these things!!)
cpu (2.8ghz athlon)
graphics card (dont want on board shat....256mb nvidia minimum)
heat sink / fan (??)
power supply (500w min)
512mb ram (PC3200 DDR)

any recommendations/advice?