A Pi-based whole house system

[tannaroo]

Technically yes but seriously NOT WORTH it. The lag on TV will be 2-3 seconds minimum and therefore unbearable.

Get a normal amplifier with multiple line inputs. Plug a Pi/LMS into one of its inputs and TV into another. Switch inputs as required. This is the only way you will get TV sound without unacceptable delay.

Can you recommend amplifier where I could plug a Pi/LMS into one of its inputs? How would I be able to 'control' the amplifier and switch between TV sound and LMS?

My current setup (which I inherited) was an Opus multi-room system with big clunky amps scattered around the house and this is what I want to replace (in fact some of the equipment has now broken).

[d6jg]

Can you recommend amplifier where I could plug a Pi/LMS into one of its inputs? How would I be able to 'control' the amplifier and switch between TV sound and LMS?

My current setup (which I inherited) was an Opus multi-room system with big clunky amps scattered around the house and this is what I want to replace (in fact some of the equipment has now broken).

Any stereo amplifier with remote control. Switch with remote so will need line of sight.

[tannaroo]

Any stereo amplifier with remote control. Switch with remote so will need line of sight.

ok. what connection/how do I attach my Pi/Hifi Berry Amp to the stereo amplifier? HDMI?

[chill]

ok. what connection/how do I attach my Pi/Hifi Berry Amp to the stereo amplifier? HDMI?

The Hifi Berry Amp would not be needed in this case. Audio out from the Pi to the stereo amp can be achieved in various ways. It depends on the capabilities of the stereo amp. If the amp has a USB input then that's probably the easiest: USB 'out' from the Pi to USB 'in' to the amplifier. Alternatively you could replace the Hifi Berry amp with a digi board, which would likely have coax and toslink outputs depending which one you get. Or you could use a DAC board to provide stereo analogue outputs - probably the most compatible with any conventional analogue amplifier. You could even use the 3.5mm jack output from the Pi, but the other options would likely give you better sound quality.
*EDIT: And not to ignore your suggestion - HDMI is also a possibility if your amp supports that as an input.