My HT/family room has a 58" Panasonic S1 and my seating is ~12' back, my mains are ~11' feet apart and I think everything sounds great. I do wish the 58" was at least a 70", not that the 58" looks tiny bit you really don't get the movie theater experience and I think the 70" would still look a little small for an HT experience but it would work very well for the general use I put my system through.

Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70