I have no basis for comparison for the particular model of Denon mentioned. People on this site seem to be looking forward to DPL II, which the 2802 has, but the 1050 doesn't. If MSRP I saw was $799, which is significantly different than $499, however. If the dealer price was $499, though, maybe that would require some thought. I imagine the 2802 has pre-amp outputs for all channels, but if not, it would be a deal breaker for me and a lot of people who want the flexibility of adding a power amp if desired.
As far as the 40 x 13 room, I don't even think my 3 bedroom house is that big. . . j/k
But seriously, I am in an 'L' shaped room which is 24' X 26' (living room) minus 14' x 12' (kitchen area with large openings to listening area) and 10' tall ceilings. Not nearly the same specs as a 40' x 13' x 13'! But, I have 87 dB speakers and have added a power amp (125x5) which is more than enough to be in the 100 dB zone at the back of the room (26' away). As speaker efficiency is so critical (3 dB is the half power point), if the speakers you are considering are in the 90+ dB zone, the 65 watts on the 1050 could yield pretty stellar results, I would imagine. If not, the 1050 does have pre-amp outs to run an external amp.
To be honest, I would seriously audition both the 1050 and the 2802, if the prices were exactly the same and the 2802 had pre-amp outputs.
In case you haven't done it yet, one of the most important investments I made in my system thus far was the analog Radio Shack SPL meter. Its $30 that takes a lot of the guesswork away from level setting and also can help when doing an A-B comparison with other products. I always test at the same SPL, regardless of other factors.
Best of luck. It is an addicting hobby.
S.