How tall and how heavy are you?
With a 10.5 boot, you do not necessarily need a wide board, although it depends on the actual specs of the board you're riding. I have a 10.5 boot, and I'm riding a 152 Stairmaster Extreme, not even the wide version. Granted I have a 250+mm waist width, so it allows me to do that, but depending on the board, you may be able to ride a normal sized deck without having to buy a wide deck.
Wide decks, especially ones in 160+ sizes, are generally reserved for size 11+ feet, or freaks of nature