The big disadvantage with pre wired systems especially in older properties is that the rear speaker cables are too short to get the recommended speaker set up as the instructions. With some systems there may be a difference in speaker size between the front and rear speakers (more high end brands such as pioneer) but most will have four or five speakers the same size (usually wideband midrange). Would find main amp unit does not have much in the way of fault tolerance due to speaker misconnection.
