This is pretty easy IMHO out of those three given your room and partial use during some ambient light. The Viewsonic smokes all these in brightness when you consider bright + accurate color, and it would be my pick for several reasons, but it'll be so bright at first you will need an ND filter which tames the brightness. The ND filter is only an extra $50, but you can get cheaper ones. You will be able to remove the ND filter after about 200 to 400 or so hours on the lamp.
Whenever you blow up an image that larger than on a TV, you will notice defects more in a poor signal (even on cable), but it can compete against a TV for a bluray disc, and more importantly the overall immersiveness of the larger image blows the TV away. Black levels and dark scenes won't be quite as rich on the projector, but immersion is the key.
The 8350 has darker blacks than the Viewsonic and better placement flexibility, but the Viewsonic is sharper and better for gaming. DLP has better motion for sports IMHO with a clean signal, but motion isn't really a factor on either for most people. The Viewsonic has a higher pixel fill over the 8350, meaning a smoother image. The Viewsonic cannot get dust blobs. I prefer the PQ of the Viewsonic over the Epson because of the more film-like image (VS is smoother and sharper), but a case could be made for either since the 8350 can do darker blacks with the IRIS (although not hugely darker). The Viewsonic has a 3-year warranty.
The Viewsonic has better color OOTB than the HD20, and probably better than the Epson's if you compare it after 1000 hours on the lamp. The Viewsonic calibrates nearly perfectly (and is actually very good OOTB with a red push in dark scenes that fades away completely once the lamp wears in). The Viewsonic lamps tend to last longer and stay brighter longer, but so far there are very few lamp issues in the Viewsonic thread. I can tell you this, at 1300 hours on my VS lamp, the thing is still brighter than a new Optoma hd20 and far brighter than the Epson 8350 in best mode.
The Viewsonic has to be ceiling mounted, but it should fit just fine in your room with no adjustments.
Keep in mind different projectors have different zoom and throw abilities (some require more space for the equiv image). The Viewsonic does it more easily than the hd20, and even though the 8350 has more mounting flexibility, it is MUCH larger and the fans are in the back on the 8350 so the size of screen you can do is about the same from your distance, and the hd20 is probably too tight of a fit. The Viewsonic's smaller size and exhaust and intake being on the side instead of the back is an advantage though. I wish all PJ MFR's would put the fans on the side.