The OP I believe didn't mention his source(s). ...Only that 95% is dedicated to home theater duties. He's also an old man from what he said, and 3.1 is his speaker setup...no surrounds as it sounds weird to him.
He has a nice Rotel AV receiver (RSX-1057) and some nice bookshelf B&W speakers (Left front, Center & Right front) plus an Outlaw sub.
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https://www.soundandvision.com/content/rotel-rsx-1057-av-receiver
That's it. I'd like to know his movie source as it's the bulk (95%) of his listening/watching.
...And the connection he uses.
The Rotel is a 2006 model, so for movies it is Lossy multichannel 3.1 (no hi-res audio codecs supported thirteen years ago).
Then Toslink and Coaxial connections are it for Audio.
And the HDMI for video, or both.
We know not much @ all on his setup, and exactly what kind of improvement he's looking for.
Why a new amp for older ears; to turn it up louder and cleaner ... the Lossy audio transmission from what ... DVD?
If he wants to share more on his setup perhaps we can discuss in the right direction?
....What best help we can suggest. To me it is an incomplete set of information.
If I was into movies, wanting a good sound from them, I would upgrade to Blu-ray with Lossless multichannel audio...a Blu-ray player or hi-res movie server or hi-res movie streaming, a new modern receiver or pre/pro (some are only $399), perhaps a Universal 4K Blu-ray player like the Sony UBP-X800 ($199), fully loaded to play anything ultra high definition video and ultra high resolution audio.
Adding an external 3-channel power amp for $2,000 wouldn't be my first option.
Not in the situation he's in right now.
So, I think he is quite restricted in the informations he provided. It is simply incomplete.