Upgrade choice?

[Buetzel]

i think your upgrade plans are fine.

i personally went with 12gb ram (2gb per instance - which is the maximum wow can possibly use for one instance, also fiveboxing, which leaves another 2gb for the os) - but that never maxes out. i think i see around 8gb used with wow - using isboxer with instant switch, so basically running 5 instances at 1680x1050 and a lot of addons on all instances (i don't disable those for slaves).

i also switched to a geforce gtx 460 (factory oc'd one), as i wanted to use directx11, but my card before was a rather aged 8800 gts 512. so i think you could still wait with a gpu upgrade.

as to specifics:
cpu is a fine choice. probably the best bang for the buck at the moment.
edit: just saw you plan on oc'ing the cpu - so make sure to get a good aftermarket cooler or even watercooling. i would check tomshardware.com for a decision on which one. perhaps more oc'ing-savvy people might be able to recommend a better source for cooling reviews.

board is mainly a preference question of manufacturer and features like raid, i/o options and stuff. i´m running an asus p6t se myself. it's okay i guess. your choice here seems fine to me.

ram is something i never seem to get right. just be sure to look in the list of compatible ram modules for that asus board on the asus website. saves a lot of trouble.