listening pace

I say "space" because this is no room I am thinking about.

I am planing the construction of a new house and considerations about energy-efficiency (thermal mass, solar heating, etc), costs and material/building method force me to work without a proper room : this will be an *open air* building.

40 foot long. 20 foot wide. Two stories.
First floor will be surrounded by a massive straw-bale/concrete (2 inches thick) wall. Ground will be thick wood planks. Sealing will be made out of the same wood planks that will be the second floor.

Above second story, a 25-30 foot gable (wood again), in wich I think to install a 15-18 foot mezanine.

I thought I could put my system on that mezanine, speakers facing void with sound absorbing pannels behind me on both sides to silence all that emptyness and to stop the sounds from coming back to my ears after hitting the wall some 25 foot from there.

It is either that or putting the system in the living room, between four concrete walls... (wich might not be that bad -- you tell me --, yet I would like to have a dedicated space).

No plaster, no paint. As soon as you leave ground level, it is all wood. -> I tought wood and lots of air might give a neutral acoustic without any specific arrangment.

System is really just mid-fi (amc integrated amp, Energy xl:16 speakers, Sansui sr-222 turntable, etc.), but if I am no *real* audiophile, I still care about acousitcs and try to enjoy it, and nothing tells me I will never have budget for a better system.

Thanks for your help -- this thing is a big project and I look forward to doing it right.
Thank you also for going through all this pseudo english I try to write :-)