Is a home theater even worth it or doable?

Oh yeah!  Movies thru a good system is a blast. I have the Sony Bravia 86 inch and recommend it. Using a preamp for 2channel music and a pre/pro for movies and TV. Both share the power amp and front speakers and a subwoofer, integrated thru the preamps. Have two side surrounds which adds up to a 4.1 system - no center channel. 
 

I tell people I don’t go to the movies anymore because the sound is better at my house. And I can stop the action and go to the bathroom when I want. 😉

interestingly, movies and TV don’t tax my system as hard as 2channel music does 

I think home theatre is very enjoyable and not that hard.  While my 2 channel system is what I consider high end, my home theatre is relatively  standard wtih a Denon 4700 HT reciever.  I use pre out from the Denon into my 2 channel amp for the front speaker and then have relatively inexpensive speakers ($1000 a pair or less) for rears and surrounds.  2 relatively inexpensive subwoofers and Top Gun sounds like I'm on deck.  

Good luck,

Jerry

If you are considering an 85" TV make sure to check out short throw projectors, they work great. Smaller footprint, bigger picture, more value:

https://www.digitaltrends.com/home-theater/best-short-throw-projectors/

You should get a receiver capable of 7 bed channels, 4 height channels and at least two subs like the new Onkyo, Denon, or Anthem.

Then start with as many speakers as you like and simply add as budget allows, no need to go all in at once. KEY- all speakers should be same brand and ideally same series. I prefer monitor speakers with subs instead or towers but YMMV.

As for HT speakers these THX Ultra2 by Klipsch would be at the top of my list to partner with a receiver. :

https://www.klipsch.com/products/thx-ultra2-home-theater-system

I started HT 5.1 since 1990. I had walls of equipment and still love HT experience.

There is not much sound difference between HT 2 chs and Hi-Fi 2 chs audios. They both have veil, glare and un-natural sounds. I think HT is much more enjoyable than 2 chs because in HT, I don’t have keep track for sound details, images, and stage like 2 chs. HT gives me everything in sound that I can truly relax (or exciting) and have a fun. Unless you must listen older CDs, you can listen so many music and movie in the internet.

I wouldn’t started 2 ch audio seriously if I knew the natural sound in reproduction audio doesn’t exist. I found it after investing so much money in 2 chs and 3 decades of effort later. Though I am glad that I started 2 chs now because I made the true natural sound audio system. Alex/ Wavetouch audio