We renovated the basement about 6 years ago and in doing so we included a media room ('HT room' sounds so passe).
Some older pics (sorry for the larger images; photobucket's resize feature doesn't seem to be doing squat):
One thing i definitely wanted was a room to control the sound for two reasons; kids growing up watching movies with friends = loud sound in the rest of the house and secondly, so that we didn't have a room that was hard on the ears (e.g. one of those marble floors, tall ceilings, open concept, lots of echo). I just don't find those kinds of rooms bearable for everyday conversation let alone music or movies or even tv watching. The rooms i do seem to prefer are the libraries and the small bedrooms with heavy curtains and carpet.
I refer to it as 'controlled' echo.
Anyway, we put together that room and i've tested out several different speakers down there; Axioms, Tannoy, Monitor Audio.
All of them sound great.
None sound good in our main living room, a room of echoes.
In brief, my point is that although we spent money on one specific purpose that WAS 6 years ago. We haven't done a thing since. I'm interested in measuring my room acoustically for the sake of curiousity, but it is highly unlikely i'm going to do anything further when it comes to tweaking sound.
I may continue to build the system from a 5.1 to a 6 or 7.1, but that's about it for the sonics.