Go for a full HD unit, 3D is only optional - if you're in to that kind of stuff which IMHO will not be permanent.
Settle for no less than 50" if you're planning on viewing 10-12 feet away. Masyado na ngang malayo yun eh
Recommended minimum viewing distance should be 2x the size of your display.
And power-wise, hindi na nagkakalayo ang power consumption ng LCD, LED at Plasma. Very negligible na ang difference sa power savings - ni hindi mo mararamdaman un sa bill mo sa kuryente XD