First, Welcome to the Shack! Glad to have you here. I moved your thread to the DIY section.. it seemed more appropriate for your question.
Now, to answer your question:
I'm assuming that you've got the woodworking skills to build a good box based on your prior experience building boxes for cars, so I think DIY would be great for you. You can save a lot of $$ and get some great sound if you already have the tools and skills.
However, there is a lot more to designing a speaker from scratch than just picking the drivers and putting them in a box -- not the least of which is designing a crossover. That stuff is pure black magic. As such, I
highly recommend you go with an already designed kit. There are several designs that are already out there that you can get for all kinds of budget levels.
In the US, there are generally 3 major internet stores I'd direct you to:
Zalytron -- Offers the best prices of the bunch. Bad website, and the person who runs it can be a little gruff, but if you already know what you want, like I said, it has the best prices.
Madisound -- Pretty extensive selection of drivers and has several designs for all kinds of budgets/desires.
PartsExpress -- Has the highest prices of the bunch, but has a lot of stuff the others don't. Their designs, overall, probably aren't as good as the other two since (and this is pure hearsay) they lock many of their designs in to the boxes they sell. Box volume/shape is one of the many variables that have to be determined in the speaker design process.
I don't know what the shipping would be to Canada from any of these companies, so I'd suggest you also take a look at:
Solen -- click on the "Design" link and it will take you to their kits.
I have no direct experience with Solen since I live in the US, but they look like they have a really good selection of drivers and a lot of kits available.
If you fill in some of the details, we might be able to steer you to a couple of kits that'd be good for what you want and your budget.
JCD