Even a 1240 x 1024 monitor can be improved by SLIing, since SLIing starts shoving more of the graphics processing onto the other GPU and away from your system, reducing hangups, lag, stutter etc.
I'd do something similar, though I might go for a HD projector.
I'm not bothered by that, and if I am, it's usually due to the game loading stuff from my hard drive, which is probably the biggest bottleneck in my system atm. SSD's should become affordable, ffs
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Also, projectors don't usually have a high enough contrast ratio (read: they won't work in regularly lit rooms), and I'm no fan of closing curtains when playing games. Or projectors, but then, I'm probably not up to date on their quality and such.
Also, I'm afraid that PC graphics will (very) soon become obsolete, since game developers publish games less for the PC platform. Still going to look forward to Mass Effect 2 and some other games to be released on PC though.
With that in mind, I fear graphics card development will gradually grind to a halt - no games to push the technology, no market to get the technology. Luckily, GPGPU (General Purpose GPU) technology is on the rise, meaning apps that require a lot of number-crunching software (image and video editing / processing, mainly) can use them properly.