Which is the best upgrade for an ok system?
CoH doesn't support SLI at the moment (though there is an unofficial way to allow SLI). Support for it is in the pipeline, but I'm not sure it that covers 3x though. So, basically, we don't really know (or at least I don't) how SLI will stack up to a rockin' single card.
Sermon
@sermon
One of Six, Cannibal 6
While SLI might be in the works, CoH will get the most bang out of video card and system memory. You have plenty of the latter, and decent vid cards. Were I to upgrade something, I'd try and sell the 260's and get one of the newer video cards.
My Deviant Art page link-link
CoH/V Fan Videos

Yeah, I figured a single card would be better, and this particular one comes with a power supply. I was gonna use that to upgrade my kids computer or my friends computer, because he is still rocking a 7950GT.
First off, the system. I have a home-built system containing a Q6600 Processor overclocked to 3.0X4, 2 GTX 260's SLI(with tag line), and 8 gigs of ram running windows Vista Ultimate 64-bit all sitting on a 780i SLI motherboard in a CM-690 case by Cooler Master. I want an upgrade.
Would I be better off going with another 260 at around 200 bucks for tri-SLI, a GTX 470 at $377(US), or another processor? The processors I have in mind are a Q9550($280) or a Q9650($330). Out of those choices money is not really an issue. I am willing to get whichever is the best upgrade. If possible, Tech Gurus, list them in order of best to worst/little value.
It is also worth noting that CoH is the ONLY computer game I play. That's why a new powerful solo card came into play. I'm not sure they are going to fully implement the SLI and Crossfire, and even then, it's only a maybe for most games in those configurations for performance increase. Truth is, I am really kinda bored and have not upgraded in a while, and even while writing this I am kinda changing my mind.