No one can know if it will be bright enough for YOU!. The 82840 uses the same lamp as the 73 and the 92".
With a properly aged lamp and fully calibrated I get about 35 ft lamberts on a 92". I would expect nearly 40 ft lamberts out of the 82". Unless you are dealing with high ambient light levels it should be plenty. Scene transitions from dark to full white in a fully darkened room will be nearly blinding.
On my 92" I find I need a lamp every 2000 hours or so. You should be able to do better than that. You might even get away with the lamp on standard brightness. An 82 with a clear screen should produce the best picture of the bunch.
Mits WD-92840 92" DLP - Lumagen Radiance XS, Martin Logan Motion 40s, Ascend Sierra 2s
Older 58" Panny Plasma -DVDO DUO, JBL Studio 530
Pioneer AJs, PSB Images, Usher S520, JBL HLS-610, Definitive SM45, MusicHall Marimba