Hey Rook,
My seating is about 12-13 feet back from my 105 inch diagonal. My projector lense is about 13 feet from the screen.
I just looked up the min/max projector lense distance from a screen size of 120 inces, and it shows minimum of 141 inches and a maximum of 215 inches. So, you will have to mount it somewhere between 12 and 18 feet or so. Sounds like that should work just fine for your setup.
The HS51 also has pretty good lens shift capabilities for ceiling mounting and the like.
I'm a fan of Pioneer, but based on what I know of the Denon products you are looking at, you should get very similar features (Denon Link, hdmi output). And the way people on this forum rave about Denon with Axioms, I think you will be very pleased with that setup.
I also think you will be very happy with Axioms all around, and save some cash while you're at it. If you are handy at all, I do encourage you to think about building your own screen though. ALmost all of the cash you spend on a screen is to pay for the frame. I built the frame in about an hour, and another hour for my wife and I to staple the fabric to the frame. Another hour after that to add the trim and it was finished.
