Yes, 14.5' is a decent viewing distance fo a 120" wide screen. That's about as large as I'd go with the JVC projectors.
DrFunk, AVRat knows what he wants, and obviously he's done a lot of research. I point this out, because you'll really have to decide for yourself. Is CIH an absolute definite at this point? If so, I'd bet good money you're going to want a larger viewing angle. As it is, even my rear row has a more immersive angle than the above, and I don't even have CIH.
Now, you might instead consider a different PJ technology to get the extra brightness you need.
My initial reaction to the differing room sizes would be to vote for the larger one. It will give you more flexibility in arranging things, and particularly speaker placement. Let alone viewer placement. (I moved my own rows quite a bit, before finalizing). Sure, the larger room will be tougher to pressurize, but I don't worry about that with the budget, and a smaller room requires more bass trapping too.
As aforementioned, there are compromises to deal with, but
this is the screen I use in a multirow setup. If you can put the viewers in a 20 deg viewing cone, you can pretty much go as big as you want even with a JVC.
OTOH, going smaller would be an easier compromise to swallow if it was acoustically transparent, at least IMO.
Otherwise, you can save money by going with the brighter Epson/Panasonic 3LCD, or instead a DLP.
