1. Buy nothing from your installer, not even cables or (if he's pushing these you know he's a huckster) a power conditioner / surge protector. Pay him for installation labor ONLY, and that would be only for any in-wall or in-ceiling speakers.
2. There is NEVER EVER any reason to buy the sub from the same brand as the speakers. Anyone who tells you there is, is incredibly sleazy and/or incredibly ignorant.
3. You're much better off going with subwoofer specialist companies like Hsu, Rythmik, SVS, PSA, etc. for your sub. For instance, that ML 1100X sub that retails for $1300 would get eaten for lunch by a $600 SVS PB1000 Pro, let alone a $900 Hsu VTF-3.
Option A indicates that you are not married to the idea of doing housewife-pleasing ultra-thin "lifestyle" on-wall speakers. That's a big relief. But you'd be better off with any number of conventional in-room speakers OTHER THAN Def Tech.
In Canada, your best bang for the buck would be the Paradigm Monitor SE series, but I'd upgrade to their Premier 500C or even better, 600C center instead of the SE center.
SVS subs are available at a number of retailers in Canada, for surprisingly non-insane prices compared to their US prices.