I have always found it interesting that the Audi A4 and Passat are on the same frame, yet the Passat has a larger trunk AND more room in the rear seat, too. And the Audi is the more expensive. I would love to hear the explanation for that. Having said that, I have owned 4 Passat's. Here in the States I could only get one fully loaded with the MT and that was a short-lived production called the W8. The trunk space was compromised due to the 4Motion (AWD). Rumors are out that the Jetta Sportwagen is being replaced by a GTI wagon of some sort, so it may be worth researching to see if that would be available in Canada in a higher end than base, and with the MT. I fully understand the desire for MT.
Hopefully someone can chime in on the Mazda6 - I have no knowledge of this model.
Your comment about SUV's is spot on. Even with my Touareg, two sets of clubs had to be criss-crossed, without any cart. Disappointing. Chevy Suburban would fix that, but a second job is requried to keep fuel in it. Then you lose your Saturday for golf.
Research the new GTI, either a hatchback or wagon I think. Or look for a 1 year old Sportwagen TDi with MT. You will be surprised at the pep that little diesel will throw at you!