Keep in mind, the shop is telling you stuff that will make them more money.
I must admit, I think most people that have done this, have the upgraded stereo. I also have the base stereo, but have not looked into the rear speakers. I have, however, added 2 10" subs to the existing subwoofer wiring that is in the rear. I added a couple amplifiers for that, though. I find it hard to believe that the Canadian model (which is not available with the subwoofer on any models) has the sub wiring connected, but would not have the rear speaker wiring connected.
If I get time today, I might be able to check mine.....
The administrator has disabled public write access.