At the moment I have 3 55" HDTV's and I am running with 2 GTX 670's in SLI mode and it has been bullet proof. Before that I ran 2 GTX 570's in SLI and they were ok but I had occasional freezing.
I think your GTX 660 Ti would be on the weak side. My advice is to sell that card and at least upgrade to two GTX 670's and run them in SLI. I know of a couple guys that have two GTX 680's and one guy with two GTX 690's a run them in SLI.
I would stay with nVidia in the 6xx series, first off nVidia's drivers are king of the hill. You will get a few of the ATI crowd that will try and convince you otherwise but nVidia is a proven weapon of choice. I also have read of a couple of people that run 1 GTX 6xx card and having good luck.
If you want, try 3 monitors with your card and if it does not work out, then upgrade with two cards and then you can race stress free in triples. When you get back from your trip your triples will be waiting. If you can afford it go with 27" monitors, bigger is better.
I have 2 670s also but I wanted to tryout 1 first so I ordered one and then waited a few days to order the other. I had a very small improvement when going sli, and it added a few stuttering problems that I ended up getting sorted out, but was a little annoying to deal with. I think I might have gained 5FPS overall and my minimum drops didn't change at all. I still drop below 60FPS on spa in the same spots I did with a single 670.
In general one 670 performed better with iracing then the sli 670s that I have when it came to have smooth the sim ran. I never encountered a single stutter when running just one of the cards, but I do still get the occasional hiccup now and then with my SLi.
After seeing how easy a 670 pushed triples in iracing 2 of them is way overkill at 1080p. I could max out AA in the nvidia control panel with one card and run all max settings on every track excpet spa and stay above 60FPS with one card. when I ran tests for max FPS it very rarely dropped below 100 and when it did, it was in the same places that my sli 670s do now. .
As well as a single 670 runs iRacing I imagine your 660 ti would be just about as good with it. I had alot of room to spare with a single 670. And I can't image a 670 getting twice the FPS of a 660ti so you should have plenty of room.
You might have to turn down 2 pass shadows and higher detail in mirros, but I can't tell a difference running them so I turn them off anyway.
If it wasn't for me playing other games on triple screen besides iRacing i would sell one of my 670s and just use one for iracing. I wouldn't doubt if you get better results running one 660ti compared to me running sli 670s. Your FPS probably won't be as high, but it will probably run smoother. I can't imagine it not being able to stay in the at least 80s on any track but spa with triple screens.
One thing that has drove me a little crazy with running sli is the screen tearing. I never needed to run vsync with my single 570 or single 670, but when I went sli 570 I had to turn on Vsync because any tearing drives me nuts,a nd it's the same with the 670s. If I don's use Vsync it stutters really bad and has horrible tearing. I've tried ton of locked FPS and none of them will get rid of both the screen tears and the stutters. With a single 670 I didn't have it at all. I could run it with no lock on FPS and it was super smooth with very, very little tearing.
Definetly try 3 screens before you order any other cards, that 660ti should be fine for triples at 1080p.
Hopefully I can still run for points in the 3 series I was planning on running.
) I don't think I'll be able to get away for another 3hrs.
