<font color='#000000'>Hi Rob,
A lot of the questions you're asking at the moment seem to revolve around the acoustics- in terms of designing a room, as you are, they're amoung the most important, as those factors are almost impossible to change once things are built, while changing electronics and even wire isn't such a big deal (though can be spendy- btw- have you thought about putting conduit in your walls/floors set up such that you can easily pull different wire should you wish to later?).
That's why I keep reccomending Everest's book- it'll give you the background you need to make intellegent (and potentially expensive) decisions. A lot depends on what you're trying to do, your tastes and priorities. There isn't any one right answer, there are a lot of factors to be balanced, and only you can decide where that balance point needs to be.
One thing you should keep in mind is ambient noise. If for example there is a nearby freeway such that there is a constant 70db noise floor, you don't even need to worry if your amp has a signal to noise ratio of 90 vs. 100 db. If you're playing your stuff at (say) 90 db, your noise floor is only 20 down, and that ambient noise is mixing with what's coming out of your speakers- you can only hear the blend.
Where are you putting the furnace in relation to the room? Do you have A/C - in the megabuck HT installations, they spend thousand isolating the ductwork so that the theater can have environmental conditioning but minimal noise is piped into the room. Just somemore stuff for the mix.</font>
