Under the carpet or in the walls for speaker wires.
A good sounding budget system around $3,000 - $5,000, Mid-range system from $5K to $10K, high end $10 - $20K or much higher. A system anyone would be really incredibly rewarding $10K - $15K.
I would recommend a separate surround processor, amp, and speaker set. Then when you want to upgrade you can do one at a time. I’m thinking $2K, $1K, and $1K Look at Rotel, and NAD.
I have developed my home theater starting about 30 years ago. Continually improving and upgrading. I would get a large LCD screen, they are incredibly cost effective. Worth the research and effort to put into place and upgrade over time. Stay away from “popular” home theater mags that advertise the ultimate HT for a couple grand. It will not happen.