I'm not sure what part of HT qualifies a a hobby. Maybe the build up and tweaking does, but sitting and watching and listening is a bit too passive for me to call a hobby. I might well get an argument from the guy who taught music appreciation back in my undergraduate days, but it seems to me that a hobby is something that you touch.
Having said that, Part of the changes of the past 15 months (retirement, new house, new shop, new motorcycle, etc.) have included setting up a "media" room. Much of the equipment has been around for anywhere from one to twenty five years. The sound processor is a Rotel as is the DVD player. Amps are B&K, NHT and a nice little Onyko that sends audio to the rest of the house. Speakers are Energy 22 RefConns for the front and Pro 22s for the rear. The sub is an NHT. I haven't gotten around to setting up the rear center channels yet. CD player is an Adcom and the projector is Sanyo with a 110" screen throw. The screen is white paint on the imperfect smooth wall.
When the shop gets finished, the next project will be a set of cabinets to frame the high end screen (perhaps I will splurge for a new coat of paint).
Maybe the notion of constantly adding to the setup is the part that makes it a hobby. If that is the case, I'd like to get to a point where HT moves from hobby to an appliance.
...Bob
By the way, my builder (who also lives down the hill from me) built a HT in one of the houses he showed us before we signed on for him to build our house. That owner had about $250K in the setup. Now that our place is up and running and after me, my wife and our builder sitting through parts of the same film in both settings, when the lights go down, it's near impossible to distinguish any difference (although his seats are more comfortable).