the screen size you desire to have will drive most of the requirements for you. Your room is long enough to go with a wide CIH setup. If you want to do close to 12' wide, u have to go with AT screen so you can place all your front speakers behind the screen. If you want to get regular screens and have speakers visible, then around 10-11' wide screen should be good.
Panasonic AX100 with built in vertical stretch and a Anamorphic lens should get you a great CIH setup for under 4K.
For CIH setup it is safer to have cables run to somewhere close to max throw range as most Anamorphic lens give better results at longer throws. Your screen size and Projector will drive the optimum distance to have cable runs.