I mainly want it to be able to run WOW at ultra settings which im not able to do with the HD 5670 (medium settings with shadows off), will the GTS 450 be able to do this or do i need to looking at the GTX 460 instead?
yes the 5670 is not a decent gaming card... if you just want to run wow full then the GTS 450 is well suited, gigabyte released a oc edition which is impressive to say the least .. as for the gtx 460 i own the oc edition and it is only a few bucks more than the 450 ...but than its all about personal preference.
Your specs are good, but can't you save a little bit and get GTX460 instead of GTS450?
GTX460 is more powerful than GTS450 and good for a long term. I'm pretty sure you can maxed out almost everything at 1680x1050 with GTX460.