In trying to keep you around your budget I will suggest the following options. I don't know if any of these are available to you in Canada but here they are:
THIS and
THIS Sony,
THIS Yamaha, and if you can spend a few bucks more then go with
THIS Velodyne if you can get a hold of one. The Polk you are looking at would better than what you have, but I think it will disappoint you a bit by not making a tremendous difference. Bass is not Polk's forte.