Tom - Thanks for the email & advice!
Jim - It has been a monsoon here lately, I will most likely try to get up to the subdivision and get a better measurement on the I joists. From what I have seen so far, you are correct. There is no bracing between the I joists, and they seem to be spaced fairly wide at about 20" between the I joists. Is there a rule of thumb to follow or look up? Yeah the sub floor was either 1/2" or 5/8" - I will try to nail that down tomorrow as well. I will not be going with hardwood in that room, as the wife and I plan on turning it into a family room/children play area in 5 or 6 years, thus she wanted it carpeted. At that point I will move the system to the basement which will be a 16' x 24' room. But that may happen further down the road as well, thus I would like to make sure the floor has minimal bounce.
Do either of you feel that putting solid bridging supports down the center span will reinforce the floor enough? Or would you try to add a few more I joists and minimize the spacing between the I joists a few inches? If either of those are done and I am going with carpet, should I ask for another 1/2" layer on top of the initial 1/2" or 5/8"? Or does 1" thick exist and just request that?
As for the noise "isolation" I have a fairly accepting wife. She really isn't worried about me "containing" the sound much at all. Since the back wall (behind the speakers) of the listening room will back up to our beds headboard in our master bedroom I will be installing the "wide green insulation tape" ( found here :
http://www.soundproofing.org/infopages/Tape.htm ) on the both sides of the studs on that wall. The isolation tape basically seems like a gasket material that will provide for some isolation to reduce the vibration and sound transmission from the drywall to the studs and through to the other sides drywall.
Also, do either of you feel the request for a second layer of drywall will be advantageous? I was thinking more rigidity of the walls would be helpful. If it really isn't helpful to double up the drywall, I will most likely transfer the funds allocated for the additional drywall to the flooring or joists.
FYI- I do have some time to work on this for a few weeks, as our contract just went in last week, they are working on the permits now and should be breaking ground in a few weeks... so by the time the basement is poured and the framing begins, I anticipate it to be at least 6 weeks or so away.
Thanks again for all the help.