I would assume you could do this in Canada like you can here. Find one of the gas stations cops hang out at, keep a look out for a friendly looking officer, and simply ask what is legal. Make sure you take a note of his name, and then in the event you do get pulled over you can say on April 6, 2010 Officer Blue told me XYZ and it won't be an issue. That is in court though.
I'd have problems believing that you can't slap some flowmasters on there. Those laws may be fairly dated. Like our laws here in Missouri revolve around the muscle car era. Those laws may be the same and have little to do with the modern interpretation of cars.
Upon reading the laws a little more carefully, it would seem that you can change out your muffler, just can't put anything weird behind it like those bizzare whistle tips. And as far as excessively loud goes, that's open to interpretation sadly. But if you go with the likes of flows or borlas they have a fairly mild idle on a V6. I would keep it as true duals though, seems a cross pipe may get you in trouble just reading that stuff.
2004 Sonic Blue V6 Automatic ~ Daily Driver
(Standard Bolt-On's) 20 MPG
2003 Torch Red GT Convertible Manual ~ Toy
(Looks good, Sounds Good) 20k miles
You make Lemonade, I'll throw the lemons back at your face.