The bearings in those motors cannot even remotely support heavy furniture, note - the wheel and its bearings need to be
well engineered, which a good wheelchair motor set gives you.
Well - I probably made the wrong assumption that using the brackets and such meant to have an intervening shaft and bearings between the gear-motor and the wheel/hub assembly. AndyMark should be able to cover all that as well; if not, there are other suppliers.
While yes, a good wheelchair motor set would give you all of this - to do the proper positioning of the furniture would still require four of these motors, which aren't cheap to begin with, and even more insane sized motor controllers, plus 24 volt batteries, etc. The wheels are also going to be a lot larger, likely - to fit on the shafts of the wheelchair motors.
Ideally, you want the furniture to be able to translate in any direction, as well as pitch around the vertical axis - for maximum and efficient positioning; two motors and wheel combos in a differential drive fashion won't give you this on a couch (unless the room is very, very large and not very cluttered - in other words, completely unlike any real living room), while four motors and omni/meccanum wheels can (albeit at a higher cost and with more complex programming).