Can a garage serve as listening room?

You can do it, but just don't expect to plunk the system down in there and get great sound. You will have to address the "sound" of the room with acoustic tuning. A garage typically has very little soft material like your couch, chairs, carpet, etc. That being said, I can get great sound by accident in my commercial garage/workshop. Especially with live music cranked up. Not much soft in there, but alot of junk everywhere to break up the surfaces. Huge metal door... no problem. Actually sounds better with the door down. It's nothing like the presentation I get at home, but still enjoyable/involving. You may find that a garage situation chages your preference in listening habits, music, and even components. Less sitting down and being caressed by her voice and more rocking out. You're your own garage band!

Certainly, Here's what I did with mine

Good Listening

Peter

Nice big room seems to be small than coz yomamma's so big!

OMG Peter, that is a beautiful room. Is that really your garage? Are those speakers Tidal Audio?

You can definitely do what Peter did ( Nice job!!!) as I also did mine too... A tremendous amount of work but we both followed similar paths with fairly similar results though mine started as a 13.5' x 19' and the finished interior ended just a bit less than that after all the sheetrock/ walls and insulation...So, yes it can be done to very satisfying levels if you want to take on the project. Good luck.