Why on earth are people saying 580gtx sli is overkill, as he's shown with a SINGLE game, there can be a huge difference at any res.
100fps in ONE GAME or even a few games doesn't mean completely playable in everything ever.
THeres more than one game now that won't be silky smooth with max settings on a singel card, and I'd expect there will be 3-4 games out this year, minimum, which will run noticeably better on sli vs non sli.
yes, MORE games run poorly at higher settings, but that doesn't really matter, I'm happy with the one card at the moment, I had 2x5850 before but wasn't loving the heat/noise but thats largely because my room is horrifically hot in summer and less heat and noise is appealing.
Anyway, for years I'll generally keep a computer that will only have issues once in a blue moon performance wise, had I loved Metro 2033 I would have gone to 5850 xfire sooner, but it was "meh" and in no way important.
if it was a game I intended to play several times(single player) or an MMO I intended to play several times a week I would get whatever cards were required to play it as I wanted.
Anyway to the OP, best option is to change mobo's to one with better spacing.
You've also got a few options with your current setup, firstly get a couple rubber washers and put them between the cards at the end, theres quite a lot of leeway between how cards sit in the slot, the top one can angle a fee degrees up and the bottom a few degrees down, that would get more air to the top card. Then you can always play around with undervolting your cards, they may run fine with a little less voltage, but only a little less voltage could mean a decent drop in temps and noise.
Maybe underclock a little to get voltage down as much as possible, because 2x700Mhz is obviously still better than 1 x 782Mhz card.
I would "hope" that Rift post launch will get a little more into optimisation and some better drivers from AMD/Nvidia while at the moment they are mostly focusing on bugs and balancing.
Basically anything, any single card or dual card setup is overkill if you don't use it, if you do, its not overkill, its really that simple.
