"Investigation of upgrades led me to the conclusion that a new computer was going to be more cost effective in the long run." ---- Well I don't know about that. You've ended up spending loads of money on your new i7 PC...lol. Why do you have a 1500 Watts Power supply? That's too much.
Anyways, regarding your problem, dell or samsung monitors are pretty good. You just simply need to check if they support 57 Hz.
My investigation was based on cost of upgrade/new computer.
750w PSU wouldnt be enough for 2 GTX280's, + another 300 gig raptor HDD as mine was full, and MoBo was having power supply problems to USB connections. (G25 and Steelsound headset sapped too much power and only one would work without a powered USB hub)
Adding ram and upgrading the the chipset + the other bits was only about $1.5k cheaper than the new computer which would still be faster than the upgrade.
I now have the ability to 3x SLI, add much more ram and overall have a computer that just ticks over as opposed to screaming, which in theory, should extend its overall life. So it was a case of do it now, or upgrade, and get a new system later.
As for the 1500w PSU, I agree its overkill, the 1200w version was unavailable at the time with little increase in price for the larger unit, so it was a case of, just do it, I want it now..... :D
As for monitors, Dell seem to be a bit more expensive in Aus than Samsung for no obvious reason or gain, and having to run older drivers with the 280's so the samsung 24's will work seems limiting when the 26' samsungs work with all drivers and are only $100/unit more than the 24's. My biggest problem ATM is finding someone who has them in stock at all, let alone 3... :?