This post is kind of old, but it comes up in searches, so I will add a few suggestions; hopefully, turn this thread into a resource for future use.
Sunlife is a big one, as you have already mentioned. But it seems geared more towards larger companies and group benefits. When I was with a large employer (about 200 employees), Sunlife was the company that supplied the extended health and medical benefits. They gave us three packages of options from which to choose. We had the option for a LOT of coverage.
Sun Life Extended Medical Insurance
Blue Cross seems popular among smaller companies. Their premiums are pretty low, and they have a deductible. I have been with two companies that used Blue Cross and I always seemed to pay the first X dollars before the plan kicked in and paid the balance. But for individuals, their rates are among the lowest.
I am now with an employer that uses Green Shield. I do not know how their rates compare to others', but their coverage is more complete than Blue Cross (perhaps my employer selected a plan that was more generous with benefits?).
If I learn of more plans, I will try to remember to add them to this thread, for the added info.