8800 GT SLI or single gtx 285/295 or ati

I am running 2 x 8800 gt in SLI and was wondering if i would get a decent fps increase going to a gtx 285/295.
I am using a 26" samsung at 1920x1200 res and can't max out my settings playing wow and get more than mid 20 fps in major cities and raids.

Will the single 285 increase my fps or be about the same in WOW.
I am sure the 295 would, being a dual gpu card, but the cost is 500 for that one and I can get a 285 for 350, and maybe go SLI later with the 285's.
That being said I could spend the 500 if it is indeed worth the increase and not having to buy another card later.

I am running a 5600+ and will be replacing the chip with a PII 940 as well at the same time.

Any thoughts, suggestions, real life experiences changing from my setup to the above setup would be greatly appreciated.

I concur with dirtymountain.
By running 2x 8800 gt's in SLI is a big deal, not to mention you have mad performance underneath that chassis of yours. No need to upgrade anytime soon, unless your playing high end games beyond 2400x(whatever the number) resolution.

I say your graphic performance is solid