Good point.

Pre amp is the TV - basically we simply want better TV sound. So variable audio output from the TV via RCA cables to a small 2.1 capable amp to drive the Polk bookshelf speakers. I unfortunately do not have the exact max size measurements for the space where the amp can go. However a 'regular' size HT receiver like the Denon 3808 is probably a bit over the max - my in-laws would prefer to keep it small and fairly unobtrusive visually.

Dan
On-Wall M5HP LCR, QS8 & EP500 in 7.1