Lex1337, how much money do you plan to spend on this total? If you get a new mobo, you're going to need a new cpu, and probably new ram (and you REALLY need a new mobo).

Also, instead of getting the PSU you have selected I highly recommend either

$69.99() PC Power & Cooling 610W

or

$74.99() Corsair 650W

Also the eVGA GeForce GTX 260 Core 216 is $20 more than the GPU you have selected, but better.