As far as I can tell the KSS-III class of subs from ROK would be the frontrunner. Last year Babcock, the company that provides maintenance for our current subs, signed a contract to cooperate on the deal with Hanwa Ocean. It's one of the best conventional subs, it has 6xVLS with the next block stretched and supposed to feature 10xVLS. Also, it's in production, which could mean relatively quick turnaround once they were ordered. The fact that it can deploy the Hyunmoo 4-4 ballistic missile is also a pretty big deal. If Canada were to be faced with a hypothetical scenario of a powerful belligerent dictatorship, stealthy submarines with ballistic missiles could provide interesting options for credible deterrence.