I know I'll probably get laughed at for this, but I had a 10-inch Bazooka in my previous car, and I really enjoyed it. I picked it because it was cheap, and it would come right out again when I wanted it to by just unbuckling it. It was also small. I had it mounted horizontally against the rear seats. It wouldn't stand up to more high-end equipment, but then it was way cheaper and simpler. I wouldn't hesitate to recommend it to someone looking for a more satisfying level of bass to compliment OEM speakers at a reasonable price.
As a fellow Canadian, I'd say look out for Future Shop slashing the prices on them. The 10 retails at $240 usually, but they go on sale frequently. Just a couple of weeks ago, I noticed that they were cut to like half price. An all-in-one 100-watt 10 for $120 is a pretty good value in my eyes. It's not for everyone, and a lot of people have a really negative knee-jerk reaction towards them, but I was satisfied with it, and I have pretty high standards for performance/value in my audio equipment.
Honestly, though, the next time I put a sub in my car, I'm going to spring for something bigger and better, since I'll be driving a much nicer car that I'll be keeping for longer (that being my Focus). Also, I enjoy trying different configurations and brands.
So that's my input, and please don't laugh at me!