So I built this system a while back to be the be-all and end-all of 5 box WoW multiboxing. At that time pretty much every part was top of the line. With Cataclysm, I know it's now a little more dated, but it still does a top-rate job for the most part. I get max fps at 60 foreground and 30 background 95% of the time, but I have noticed that when I drop 5 sets of totems I lose a massive amount of fps, and it gets hard to control. Where can I improve for the best bang for buck?

ASRock X58 Supercomputer Mobo
Intel Core i7-920 Bloomfield 2.66GHz
CORSAIR XMS3 6GB (3 x 2GB) 240-Pin DDR3 1600 (PC3 12800)
Intel X25-M Mainstream SSDSA2M080G2XXX 2.5" 80GB SATA II MLC Internal Solid State Drive (SSD)
BFGTech GTX 260

I don't get model-loading lag in Orgrimmar except in very rare circumstances, usually during prime time, and I don't consider that a deal-breaker. My first impulse is to say my video card would be the best upgrade, it's probably one of the more dated pieces of the puzzle. If so, do I need to go overboard with it, or are mid-range cards going to give me more than what I need for this application?

Also: Should I consider overclocking the vid card before I replace it to squeeze out the performance I need, or is it not a good candidiate? Keep in mind, I don't believe it's worth anything because resell value on video cards isn't exactly a factor, so it wouldn't bother me to blow it up and get a new one...