multiple monitors-multiple GPU/video cards

This is my first post on this forum and I pretty much joined to ask this question of you. I will soon be building a new workstation to do editing/processing and printing from and I want two calibrated monitors. I have one calibrated monitor on my system now. The main reason I want two is to do work on one and then view the results on another at full screen without closing things down and then not being able to compare the two. Also being able to rotate the 'display' screen will be nice. I do recognize that it will be difficult if not impossible to get the two to look exactly alike but I can deal with that.

OK, here's the question. Are any of you out there running two separate GPUs one for each of two monitors and what if any issues are you running in to. The GPU that I'm using now, and I understand this is true for most, is that there is only one LUT entry that us used to calibrate whatever is connected. You can calibrate one or the other but not both at the same time with different values. There are supposed to be GPUs out there that have two LUTs but I sure can't identify them.

I'm still running XP and for the most part is does what I need but I will have to admit that it's just getting left behind and I will probably build some kind of multi-boot system; Windows 7 or 8, OSX and/or a Linux. Each one of those operating systems have their charm.

So besides needing something more beefy in a PSU what else could go wrong. Is anyone else doing this?

This may should have gone under calibration, but I thought it had more to do with hardware that actual calibration which I don't have TOO much trouble with.

Thanks--Michael

I have ran up to 4 LCD panels.

No issues other than:
1) when I did this on low end PC, power supply couldn't push enough and crashed often
2) I tend to lose my mouse cursor!

On my current one, I'm running one monitor each for two graphics card I have. No issues what so ever. It's probably cheaper for you to get two inexpensive graphics cards than get one with two GPU on a card.....

For calibration, I use Spyder line of products. I've heard, with latest software, they solved the issue of LUT with multiple display setup. But, since it doesn't apply to me, I don't have any details.