If you're really going to upgrade, then Intel is the way to go.
I do think you'd be better off waiting a couple months and saving the literally $60 or $70 extra it will take to get an i5. Dual-core processors are disappointing, and the FX series have to be pushed to be good.
Upgrade paths have a funny way of closing in three years to where you'd need a new motherboard AND a new CPU. Of course, you could always upgrade to the current-gen i5, but why not get it all taken care of at once.