The way my house is built is rather unconventional. The living area is open to the dining area, but in a diagonal fashion. So the way it is set up now, there is no rear wall. The speakers are about a foot and a half away from the side walls. The side walls taper out away from where the system is set up. And yes, the house is all block and plaster.
Before I begin to rearrange again, I'm going to try these two suggestions. First, move the speakers out another foot to aleviate any interaction from the television screen. Second, fire the speakers straight ahead instead of toed in and hopefully, this will minimize any reflections from our coffee table.
As far as speaker cables are concerened, I'm upgrading from a 3M set of revision I red dawn cables to a 2M set of Revision II Red Dawn cables. Before receiving my quattro fil XLR's, I was using "the best" radio shack RCA's (they were temporary, don't flame) and it was a huge improvement moving up to the quattro fil balanced IC's.