If you are considering Green Mountain Audio speakers, call Roy Johnson. He is a master at placement with all the soundstage work he has done in the past. Your room is tough. The Callisto's are bottom ported and can be close to the walls, but Roy would be the one to ask on placement. Maybe the new Pico would be better or the Europa.
Good luck!
http://www.greenmountainaudio.com/Speakers/BookshelfStandMounts.htm
Good luck!
http://www.greenmountainaudio.com/Speakers/BookshelfStandMounts.htm