Try the Omega Super 6 XRS Alnico or the Super 8 XRS Alnico. They are designed with a down fireing aperiodic port, so distance from the back wall is not that critical. Also Louis at Omega is a one off custom builder. He can make any of his designs with a front port to compensate for rear wall distance. Give him a call he is a great guy and is very passionate about his designs.
(203) 847-2800
http://www.omegaloudspeakers.com/products/super6series#6xrs
(203) 847-2800
http://www.omegaloudspeakers.com/products/super6series#6xrs