Did you run the benchmark -- what was your score?

FFXIV is pretty CPU intensive so you probably won't see alot of performance increase by just upgrading your video card since you have an older dual core cpu.

So I would just recommend getting something that is a good boost but nothing that you'll be throwing money away with. Like:

http://www.newegg.com/Product/Produc...82E16814102988

A 6670 for ~$50 should give you a good boost but your CPU will be the bottleneck at that point so anything more powerful is just a waste.