Well, the "where to buy" determines what is available, so that can be important as well. Best bang for dollar is SVS but that will be at the top of your budget. The ported SVS PB-1000 Pro is $1099 on
electronicsforless.ca while the sealed SB-1000 Pro is $829.00. I went with the sealed SB-2000 Pro because I needed something smaller, but the ported version will perform better at the lowest frequencies. If those are too big, they have the PSB Alpha S8 on sale for $599 but don't expect any 8" sub to perform as well as a 12" SVS subwoofer. If you move to to an 8" or 10" driver there will be some compromises. The SB-1000 Pro is a 13" enclosure so if that is the right size, that would be my recommendation for new models. With subwoofers, displacement matters so go as big as you can and ported models if you have space.
On the used market, my preference is
canuckaudiomart.com. You can narrow the search to QC and ON. Kijiji can be hit and miss and you need to test everything before buying. I have had no issues with sellers on canuckaudiomart. I do not see used SVS subs for sale very often, but used you might find a nice Paradigm, PSB or RSL. You can post a link to the ad and ask for advice here.
Avoid the cheap subs from BestBuy. I started with a 10" Klipsch for $250 and it was a waste of money. You will get more enjoyment and longer use out of a quality brand like SVS, RSL or Paradigm.
