The limiting factor will be your playback environment. The question of "is X worth $2000 more than Y" is no for most people. To really get that upper tier performance acoustics becomes very important. Acoustics not as in absorbers (which everyone assumes encompasses acoustics in a nutshell) but EVERYTHING sound based.
I'd suggest you first invest in research, and buy a solid resource book like this:
http://www.amazon.ca/Handbook-Sound-Studio-Construction-Recording/dp/007177274XIt will teach you everything you need to know and more in plain language. It covers everything from a sound reproduction focus. The title is misleading, it is not solely for recording booths at all. There is a chapter dedicated to home theater design and every other facet of construction (including acoustic assesment, treatment use and construction.)
It is not solely construction based either, they use the term construction loosely. I would term their use as "creating" more than "constructing." Many of the room plans and methods are based off any existing domestic space. This book would benefit anyone who is interested in the goals you are presenting. You would likely never have to build a bigger room (unless you want to fit more seats.)
Its $30 that stopped me from googling what to buy and what to do questions.... ending up in forums and reading 20 answers from opposing viewpoints. Most of whom do not have a clue of what they are talking about and regurgitate what they read in other posts. (Not here usually, before anyone gets upset.)
