I've gotten more bloody speedy tickets on the 401 than I can count. Mostly late night speeding romps.
Best snow tires, IMHO are Nokians. I agree with the previous post. Expensive though. So I use Toyo Observe snow tires. Also excellent and close to on par with the Nokians as far as grip, treadwear and noise go but about $30-40 cheaper per tire. I've used everything from Crappy Tire Nordic tires to Michelin Artic Alpins to Blizzaks. The Toyos are far better. I paid $140 each installed for 195/65R15. Continental snow tires are not very good, I've used them.
In fact I have four slightly used Continental Super Contact tires available. P185/65R15. All four are yours for $100 if you want 'em.
For summer use, and for high speed driving, I use AT LEAST an 'H' rated tire. Preferably a 'V' rated. If you are getting that high speed wobbling, I'd put my money on the tires. I'm currently using Toyo Proxes H4 for my summer use. They're very rigid and excellent at high speed. Of course, they're crap in the snow so come November, the Observes go on, whether or not there's snow yet. The Michelin Pilot series is also an excellent tire, but I would definitely go for the 'V' rated. As was stated, the benefits of a HIGHER RATED tire can be felt immediately. They are more stable laterally and less prone to wobble at high speed. Very important things if you indeed travel at high speed occasionally...if you have to brake suddenly at high speed, you'll want good tires...
At 200 KPH+, the Proxes H4 are as solid as a rock. Myself and a couple OPP officers can attest to this.