I am at 12 feet and the 65 is just a little too big, but I am switching to the 57 for other reasons. I have already had a 57 in my house before I bought, and it seems a little small at 12 feet. I agree you are on the close side, but don't think that you are too close to make it work. The set at CC in my neiborhood is 7 feet away and I never thought I was too close.
I would try and talk you over to a TWX or SWX though because after owning the xwx, I don't really use the decoder much, and firewire seems only for interconnecting components now and nothing to do with possible copyright protection, which was still up in the air until the end of last year. Once I factored those 2 out, I am left with 1500 for really nothing. I decided to use 500 of that on having it calibrated and pocketing the grand. If you can find a TWX, it will have the nice cabinet like the XWX only marble instead of black and the XWX screen, and it is only 200 more than the SWX. I know the XWX 51 is just coming out, but have not seen it at a dealer yet. If I were you , I would get the 57 and get it from somewhere that has the 30 days for return, and if you decide otherwise you can always go down in size. I had a problem with going from the 65 to the 57 because the 65 is more cinematic, but when I watch a 51 at no time do I feel the movie experience, so there is a huge incentive to make the 57 work.
In closing, so you basically don't want yourself to be overwhelmed by your new top of the line, High Definition, best analog on the market, only model which will allow split picture dual HD for sports, Rear Projection Television, is that it? That is a dilemma you surely don't want to face. You can't go wrong with the XWX, but I think you will find you don't use the OTA much, and cabibrating on the other hand does seriously help, so if you can avoid it, I just wanted to share my view after I bought. I shared your view before, but at that time it wasn't as abundantly clear that firewire is never going to be the copyright protection method, if that comes to pass. I tried many sets but in the 51 and 57 model, there is nothing that I have seen better in HD, and I was very suprised that these sets are stunning in analog while all the sets they compete with on the HD side, are just horrible in that regard. If you haven't already noticed that, then you will be getting a bonus when you do. I hope you get the set that is best for you, but also hope you decide to try the 57 inch first with either the XWX or the SWX/TXW depending on dealers in the area.