Been a while since I've logged into Azeroth, I blame it on the the lack of 5 shamans being able to burn through low level northrend instances but in reality its my system not being able to handle nothrend, v.v so my current system specs are:

CPU: Phenom 2.8 (forget the model >.<)
Ram: 8 Gigabytes of DDR2 800
GPU: Nvidia 8600 GTS SC
HD: 320 gig Seagate Sata

I assume its my GPU stopping me from 5 boxing, So I'm wondering whats a good route for upgrade to make this system 5box worthy? I was looking at maybe a 4890 or a 260, what does the community think? will this get my system up to par?