Update on my situation. Took jmask5's advice and called Crutchfield, as I thought Sennheiser Canada's response (ship us your defective bar, but don't expect us to tell you when we will reopen and fix it for you) was crap customer service for a product priced pretty much higher than anyone else's. Crutchfield shipped me a new bar before I had even had a chance to return the defective one.
The night before I planned to ship back the defective unit, I was awoken at about 2 am by a strong, electrical burning smell. Long story short, it was the defective soundbar attempting to catch itself on fire. The right side of the unit was too hot to touch, visibly smoking. Thankfully, no fire resulted, and by some miracle there was no damage to the wooden entertainment cabinet it was resting on.
A couple of days later the new 'bar arrived. So far it has performed fine. Needless to say, I am VERY nervous about the new 'bar as well: it is one thing to have a well documented defect with the centre channel becoming muffled, but quite another thing to have this product try to immolate itself.
Let's just say that I am trying to be reasonable and open minded, to give Sennheiser a second chance, but with a healthy dose of skepticism, and a caution to fellow forum members to 'be alert' for overheating issues!