Hi Chris,
If you are close to the Sivananda Centre, definitely check it out! Great dedicated teachers, and a lovely atmosphere, beautiful hardwood floors etc. The most enjoyable satsang in town. If I lived closer, I'd be chanting there every week.
Another place that teaches very precise hatha yoga is the Yoga Centre Toronto on Young St., N. of Eglinton. A friend of mine ( a yoga teacher)started taking a class there which is designed for people with specific health issues. She loves it.
If you are after ashtanga, I have come accross some ashtanga people here in the past, just don't remember where.
Good hunting!