My only concern would be your video card. I heard that the 9600 series is not that good but I could be wrong. Just start at 800x600 and low settings, work your way up from there.

I fried my 8600GTS with a 5 box single system. It handled 2 boxing just fine.

Just make sure to clean your system at least once a month as just a little dust can screw up your system big time. It's subtle and over time it will destroy your system.

IMO I would do a quad core with at least 4 gigs of ram. I would steer away from a dual core as both cpu's are now working overtime to support a game and all the resources that are running on your system. You need more memory!!!! Wow takes half a gig to run one instance of it. Then you have windows running as well. All together that is a huge strain on your memory. I suggest getting 2 more gigs since its cheap and you might as well hit the roof on memory requirements for XP.

I would also use msconfig and kill all running apps under startup.