Drumstixkev for doing it wrong it sure looks nice lol. 

  The main problem with attaching the ceiling to the floor above is that any vibrations will travel from people walking above and any noise from below will be more easily transfered to the space above.

 One of the biggest considerations in all of this is whether you want to only have a good acoustic space to record in or if you also want to prevent loud noise from getting out. If you plan to play late into the night and have neighbors close by then the "box within a box" concept is the best way to fly,and also is helpful in absorbing waves if done correctly. 

  I think I may have been misunderstood on the idea of having a second floor over the concrete floor. The floor I'm thinking of doesn't necessarily need to be very thick. You could potentially go with a 1 1/2" -2" dense foam inbetween 3" studs turned sideways and then lay 3/4" plywood over that. This would get you up off the floor a little over 2" and you can still throw a rug down. This is pretty common in basement construction and it prevents any disaster in the even that you get a small amount of water down there. If I had 10" ceiling I would probably make the floor thicker if it were me, but it ain't ;) and "what ifs" are plentiful.

 You can get into a lot of math in building a studio especially concerning the distances of the walls. In a nutshell you want the walls to be spaced in such a way that they don't re enforce bass and harmonics. If you have common bass frequencies at say from 20-50HZ you need to calculate the resulting waves and distances and make your walls at a distance that is nowhere near that. Same for ceiling to floor calculations. The same applies to taming some of the mids. We have work arounds like EQ and products like ARC but if you start out with a space that is encouraging flat response and discouraging standing waves you may not need to tame a dragon later on in the process. Even EQ and/or ARC can't correct a really bad room.

 I wish I was where you are Bub. I'm dealing with a 12X12 bedroom here. I don't have a band so it works for me, but does get confining sometimes.

Does your basement have bats?  If there's one thing I know, it's that putting all of your high tech gear in a subterranean cavern populated with bats and featuring a waterfall is the most logical design.  It also helps to have a butler to bring you snacks, prepare your gear, and keep out the riff-raff.

A car with a rocket engine is necessary, too.  A sidekick can be useful, but he'll probably tend to get himself captured frequently.

On second thought, it would appear that I really don't know that at all.

Im in that 16x20 

With 7 guitars, the drums (5 piece), keys, desk, speakers, TV, 1 guitar cab 

And Desk is against the wall (NO NO for mixing)

Its pushing the limit of space and easily moving around things

Space down the road could be pushing it as things might get changed or added

 I hear ya on that Digi2ns...Bubba I didn't know if you were aware that Bub has the tendancy to sometimes eat people. His snacks might not be the kind of thing we are accustomed to having around the house. Lets just say we don't want to be there when he gets hungry.

 Here is a room modes calculator that might help Bub....hope I'm not interrupting lunch.

http://www.sae.edu/reference_material/audio/pages/Roomodes.htm

kev, that is a beautiful space you have there! Love the stone wall diffusion, don't know how it sounds but it sure looks good.

My own space is all about function over beauty. Some track lighting was my only concession to decor, everything else is purely practical acoustics. 

On the circuits.... the 20amp circuits should provide plenty of power. the average studio might pull 5 to 7 amps if you have lots of gear plugged in and turned on. My guess would be an amp or two for the computer & monitor and that's about it. 

If you wire to a 15a breaker you can use #14 gauge wire. NMB commonly called romex. And while many outlets still permit "back stabbing" the wire into the hole on the outlets, don't do it. Strip the wire and wrap it around the screws and snug them down. It's a much better connection. I've seen too many back stabbed wires get loose and literally burn the back out of the recpt/outlet in the wall. Scary stuff. 

20 amp circuits require the next larger #12 gauge wire. If you go to a 30 amp circuit you are required to use #10 gauge wire.  Using the smaller 14 or 12 on a 30a breaker is a code violation and a fire hazard.  Wire should be sized properly and according to the breaker size. 

Also, be aware of the requirements to use AFCI & GFCI breakers where they are required to be used by code.... again this is a safety and fire/shock hazard issue. 

Guitarhacker

On the circuits.... the 20amp circuits should provide plenty of power. the average studio might pull 5 to 7 amps if you have lots of gear plugged in and turned on. My guess would be an amp or two for the computer & monitor and that's about it.

If you wire to a 15a breaker you can use #14 gauge wire. NMB commonly called romex. And while many outlets still permit "back stabbing" the wire into the hole on the outlets, don't do it. Strip the wire and wrap it around the screws and snug them down. It's a much better connection. I've seen too many back stabbed wires get loose and literally burn the back out of the recpt/outlet in the wall. Scary stuff.

That back stabbing option should be banned. It doesn't work and creates so many points that something bad could happen.

20 amp circuits require the next larger #12 gauge wire. If you go to a 30 amp circuit you are required to use #10 gauge wire.  Using the smaller 14 or 12 on a 30a breaker is a code violation and a fire hazard.  Wire should be sized properly and according to the breaker size.

I was mistaken about the 30 amp circuit. I meant to say 20 amp.

When I built the kennel/shed at my old house, I ran 10-2 W/G from a 30amp breaker in the house, out to a small panel in the kennel. It was about ... 40 feet or so. I buried it in outdoor PVC meant for electrical then split it off at the box in the kennel. The only thing I wasn't sure of was whether to ground it to panel in the house, or run a separate ground to the box at the kennel. I ended up running a ground to a rod outside the kennel, and I hooked up the ground to the box back in the house. I talked to an electrician and he said it didn't matter, so that's how I did it, but my gut was telling me the whole time that it was wrong and that it should be one way or the other, but not both.

Also, be aware of the requirements to use AFCI & GFCI breakers where they are required to be used by code.... again this is a safety and fire/shock hazard issue.

I have a 120/240 30a circuit to my shed. I have 4 wires run out there. 2 are the hot phase legs and then I have a neutral and a ground.

It has been a long time since I did electrical work.... I do security low voltage stuff now.... but IIRC, you want 4 wires (if 240v) and don't bond the neutral & ground on the sub panel.  The ground should float so the neutral current doesn't use the ground wire as a return. 

  I believe you can run a 3 wire circuit and drop a rod in the ground at the panel.  Maybe that has changed in the newer codes..... 

To be honest though..... I had to take an online test today to renew my license....and I don't have the last 2 NEC's that have been released..... so I have not been keeping up with the changes in the codes over the past few years and I know there are a bunch of new requirements and things you could do in the past are not allowed anymore..... especially when it comes to bonding and grounding......