Which a8n board?
again, the 6600's are obsolete if you're into gaming
psu okay, i woulda gotten enermax/antec/fortron
should get 2x1gb insteadm twinx/xms is fine.
fishmahn is somewhat right about dropping the cpu if need be, although i would also drop the extra dvd-rom drive. i highly suggest not doing optical->optical direct burns, ever. in regards to the cpu, 3700+ is like $50 more than the 3200+ Venice (CG/newer revision, which sells for like $175 on Newegg, not the $160 version). I'm not sure if you really need the extra l2 cache, considering you're probably gaming and the controller on these chips are incredible.