The only difference I've found with balanced cabels is a couple db more volume. Balanced cables are only superior if your making a very long cable run.
Also, if you ever want to drive the low frequency section of the minis directly from the
990, you'll have to use unbalanced as the minis dont have a balanced input. this setup would require some tweaking of volumes anyway, but being somewhat anal, I've always tried to be consistant and introduce as few variables as possible.