cabinets for 15" coaxials?

greetings: looking for suggestions regarding good cabinet designs for 15 inch "co-axial" speakers. i just picked up some university 315s, but might be interested in trying altec 604, tannoys, EVs, great plains, etc. in the future to compare.

i use 2A3 and 45 SET amps, so need to maximize efficiency. i like healthy bass response. listen to acoustic jazz as well as heavy rock.

my listening room is medium size (perhaps 14x18 with 9 foot ceilings, rectangular but not a perfect rectangle). because of house features and furniture placement, the speakers can not be in the corners, but need to be about 1/3 of the way out into the room and a bit in from the walls.

prefer relatively narrow width, can go moderate to deep in depth, and can go tall. its on the 2nd story, so manageable weight is also a plus.

i would appreciate any suggestions, tips or experiences that you care to share.

thanks -andre