Well to start with there are a lot of good quality capable regs that will suit the bill for tech diving in Canada. For starters you are going to want a high performance balanced first and second stage to be able to provide breathing gas at depth without struggling. You are also going to want to consider something that has an environmentally sealed first stage, which will help with maintaining reliability in very cold water. A heatsink on the second stage also helps with this.
My personal preference, and I remind you this is just my opinion, is the Zeagle Flathead VI's and DSV series regulators. They incorporate all of the features I mentioned, and are very easy to service. Like I said there are many other regs that fit the bill, a few others that pop to mind are the Apeks XTX series, Scubapro Mk17/G250V, Salvo's, Diverite's, Oceanic GT3/Delta 4/Eos just to name a few. To start with I would see what is available locally, and has readily available service in your area. If you happen to be around southern Ontario, let me know, I'd be happy to go for a dive with you and let you try out my Zeagles or my Oceanic GT3's that I have setup as single tank regs.
Jim