Voiceover Studio Booth in Tight area/ceiling.. HELP!

In another 6 weeks I have to entirely re-locate my voiceover studio.. My current space is a 10x14 room that is blessed with isolation, my only obstacles being reflexions, which I have successfully treated.. My new space is in a basement... furnace/HVAC is an issue.. It lives about 25 feet above, on the first floor.. there is very little insulation from my new room to the furnace.. people walking above is also an issue.. The easy solution (3.5 x 3.5 WhisperRoom) is a no-go since the WRoom will not clear the just barely 7 foot ceilings... My most logical place to locate is in a corner of the basement, within a 7"x7" foot area.. possibly 7"x9"... I only require my mixing desk and a place for a mic stand and copy stand, so 7"x7" just might be enough.. I've attached some pix of floor plan and photos of the corner... the temporary Gobo in the corner is the proposed booth location https://www.dropbox.com/sh/054xcxtjiiowevt/R_eRqeHCt7 I would like to do this on a budget of $1500 if possible.. for a 7"x7" space, some have suggested building 2 double walls, Quiet Rock on one side and normal drywall on the other.. and then treating the already two standing walls and ceiling with sheets of Quiet Rock.. for a 7"x9" space it would seem two sliding doors would have be relocated and I am trying to avoid that. If it wasn't for the HVAC, the space is QUIET... reflections are easy easy to deal with .. I'm trying NOT to do a lot of building out because I am only gonna be in this space for 1 yr. and have to relocate again... Any suggestions, Gang? thanks.. I'm about at my wits end and I'm running out of time.

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