I had the exact same thoughts. I have the 10HT and am ordering the GrayHawk next week. It is a lot of money for the GrayHawk 135" diag that I'm getting but I also am considering the next projector several years down the road which should be crisper and darker than the 10HT. I plan on still using GrayHawk then. It appears to me that the projector is a bigger factor in image quality than the screen (ignoring the source aspect in this comparison). I'm compensating for the the 10HTs pixels for such a large image with a lens from www.cgns.com
which has worked well. (9' and 14' to answer the seating question <g> -- 14' is awesome and 9' is great).
My point? Consider the size of your screen as well for future use.
P.S. Your 3D website pictures are just slightly less than incredible (I saw them on another thread).