Yeay, a fellow Canadian!
I'd look at the Cadence X-Sub which is aval on ebay for around 290, with affordable shipping. Its a kick *** sub, but only does 25hZ, while some of the svs/hsu units will go down to 15Hz. Dont get me wrong, it is a beast, it will shake your room like no tomorrow, but if you are an audiophile, and you have a bit of money to spend, you may want to look at something that has a bit more frequency responce.
http://www.svsound.com/products-sub-box-10isd.cfm that seems to be right in your budget, though maybe a bit over b/c of the exchange rate.