The only other times I've seen the Opera House that empty were Amorphis in 2008, Green Jelly in 2008 and Enslaved in 2007. But this may have been the emptiest.
10/18 - King Diamond
10/24 - Pallbearer
11/01 - Suffocation
11/30 - Devin Townsend
12/06 - Distant Worlds: the Music of Final Fantasy