And while we're fixating on equipment, what about the room?
We built a new house 2 years ago and I got a "man cave" out of the deal. As we were finishing the basement anyway (for energy efficiency and a 4th bedroom) the room was a freebie (wiring and wall insulation were already included). What little extra I invested was easily recouped from wifey not filling it with "extra" stuff that would have gone into storage.
Anyway the room is properly proportioned 1 x 1.61 x 2.61 (8 ft x 13 ft x 21 ft), has staggered double stud interior walls, insulated fiberglass exterior door with weather seals, insulated flex duct for supply air, and three dedicated circuits for audio with cryo'd hospital grade Hubbell receptacles. The whole house is wired with 12 gauge, 20 amp circuits. All appliances are new and we have our own transformer thanks to a long underground power feed.
Naturally the biggest advantages are:
1. No WAF
2. Sound insulated, both me from them and they from me (almost spooky at first)
3. Can listen when I want at pretty much the spl I want (high or low)
4. Have both nearfield setup for critical listening and nice farfield setup while computing
5. Of course, it sounds great in here
Previously I had a well similarly sized room, but didn't have advantages #2, 3, and 4, so I had to wait for the house to empty to really listen. I'm amazed at all the examples you can read about of "serious" money invested for equipment that go into crummy rooms and/or speaker/listening position setups. That is what headphones are for (which is what I did in college).