well, I know that both myself and Stereo Mic have done both careful speaker positioning, and then gone the whole hog and used the full, complete (non-shareware!!!- important) version of 'CARA' to model the room, and ensure exactly the right speaker placement, to within milimetres of where the speaker should be.
Having done that, I know that I (and SM) have both tried quite a few brands of IC, speaker cables, and power cables.
and you couldnt hear a difference ?
quite odd really when I can spot differences in my setup and mine costs a fraction of what yours costs.
if someone was to come and change my speaker cables without me knowing , I would be able to tell something was different or wrong. Usually its in the subtle details of background percusion, how forward the vocals sit in the mix or how the instruments seperate.
each to their own I guess