TV Size (Diag inches)16:9 THX Rec16:9 THX Max16:9 Max for 1080i 404.56.35.2 455.07.15.9 505.67.96.5 556.18.77.2 606.79.47.8 657.310.28.5 TV Size (Diag inches)4:3 THX Rec4:3 THX Max4:3 Max for 1080i 404.15.84.8 454.66.55.4 505.17.26.0 555.67.96.6 606.28.77.2 656.79.47.8
that a 63" television has a THX suggested seating distance of about 7 feet. I had to go to the Viewing Distance Calculator to see that a 73 diagonal TV has a recommended seating distance of 8.2 feet. Should fit fine in that room.
Note the table Bob mentions is quite aggressive compared to usual recommendations, which is typically about 4-4.5 times picture height for a typical mix of sources. That table is based just on viewing angle (for films at a movie theater), not picture resolution (higher for film than TV); it might be OK for HD 1080i but is probably too close for poorer SD sources.
If both the set and your couch/chair are within that 15'x15' area, viewing distance 10'-11' I imagine the 65 would already be large enough. If viewing distance is closer to 13'-15' then the 73 should be OK.
The surest way of course is to go to the store with a tape measure, and watch the sets in question with a variety of sources at your actual viewing distance. Should be fairly clear to you what you prefer after a while.
Well I really new that 65" was as big as I should go since we will be watching a lot of regular cable television. You know that us guys got to get whats biggest and badest. My wife will be much happier as well, since it drops the price in about half.
I've got a 50" DLP, 10' is optimum for me watching a variety of materials. I think as with any rule of thumb, personal preferences vary. I'm speculative that kind of T.V. technology might also influence distance preference?