Advice on Listening Room/Mixing Room Buildout?

First post here, and I hope it's not too rude to just cut to the quick? I appreciate all of the information that I found here on this site (some of my questions were answered already by just poking around... so thanks). I also posted this on Ethan Winer's site.... so, if you travel to both, please don't be offended... If there is anything wrong with this post (details needed, wrong forum, whatever), let me know or just move it and I will try to find it... On to the meat and potatoes as it were.... OK..... First let me explain that this is actually a mixing/mastering room, but I have no need for it to be a recording room as well.... I have a new company doing live 16 track digital audio recording.... we also offer the service of post production mixing, mastering, duping, artwork, etc.... as a result we are in need of a good environment to do mixing and mastering. We have the Roland VS-2480 16 track digital workstation, a desktop computer, a rack of external effects (3 multi units and a digi reverb), a DBX 166 dual compressor, Rane 2 ch GE14 Graphic EQ, Tascam patchbay, a decent QSC amp and some JBL 4412 monitor speakers (NOT the 4412a's) as equipment... We DO NOT offer in house track by track recording, so having room to set up instruments and record in house is not a big concern, although I intend to record for fun in the 'extra' space I have in the basement, and no doubt work on my own things in the mixing room.... the focus here is on a good listening room to mix our live recordings in. That being understood, lets proceed.... I have included here detailed drawings of the space available, and a rough draft of the first concept I have for a decent (by the numbers) control room size of 7'6"H x 9'7 3/16"W x 11'6 5/8"L. (1 x 1.28 x 1.54) I would like advice on anything anyone thinks might help (or a better forum to ask for advice on, although this came highly recommended)... In particular, I question these things.... I don't have anywhere near enough space to make an "ideal" listening environment.... but few people do.... I do, however, have the knowledge and ability to build this room to suit, in the space available in the basement of my home (not rented or anything).... and it is a fair amount of space... This is the space I have available to me.... A larger version for viewing/printing can be found here Here is a view without the clutter of the details and some color to define things and a scale (drawing is to scale) (missing top dimension is 12'0")- again, heres a larger version I have a fixed acoustical ceiling height of 7'6", because the rafters are open to the subfloor above ( which is diag. 1" fir with hardwood above). The floor joists are solid actual 2"x10" (110 year old house). So my 'visual' ceiling height will be 10" below this @ 80". I am considering using rigid FG between the joists above and fabric to cover this to make the entire ceiling a bass trap (good idea?).... then add some reflective areas to suit? The basement floor is concrete, but can be treated to suit (most easily, just carpet) This is a basement, and my office (and current mixing room)are right next to the area I suggest using (see left side of pics). I have NO ISSUES with absorption, as I can have a full band in the basement now and barely hear it outside (thanks to 12" thick limestone foundation and sturdy old brick house build). The existing walls are already furred out from the limestone foundation by ~6" and then 2x4 and drywall . I also have the ability to build the walls 'inside' the existing room and still be a decently large room of proper dimensions (by the book).... I am inclined to build these walls to be traps as well by leaving them uncovered on the interior, thus making the drywalled outside of the wall an "acoustic interior" wall as well .... as it is my understanding that in a room this small, the more traps the better.... and since I am a contractor I have lots of knowledge and supplies to build my own (ideas welcome). Here is the concept drawing I have come up with so far.... Another larger version if you so choose to DL or look at Other sizes and shapes of rooms are options, so long as they fit into this space shown in the first two pics... A few questions I have not found answers to might include, but will not be limited to... Should I angle my new walls? How much and which way? (I can only go smaller with this configuration due to imovable objects- the boiler) What type of studs.... fir or steel? Should I bother with commercial sound channel between studs and drywall? should I remove the existing drywall and insulate behind? should I re drywall the existing wall or leave it open (lots of space) what should I use for the Exterior of the new walls (red in drawing) how about the interior? (keep in mind I think I want them to be traps with insulation in them.... cloth?) how about the ceiling? Again, it's open joists now... I'm sure I'll have more questions and replies from anyone are welcome..... so, yeah, lets see what you think I can do here.... Thanks a lot in advance..... you have already been a great help