Suggestion on IN WALL XLR interconnect

Transparent makes specific interconnects for in wall applications. See Transparentcable.com Hope that helps...

i'd not myself bury any interconnect in walls. if possible, you might think of installing fairly large plastic conduit in the wall so that replacements might be made in the future. for your application, i'd recommend cardas neutral reference. it really does work in long runs. i use a 21' pair (balanced) between pre and amp in my system.