Had an old passive sub that I rigged to run for my Marantz SR8002 receiver for a little while (mostly just to prolong the current setup until I moved the equipment to a dedicated HT room). Now that everything is settled, I wanted to get some takes on what type of subwoofer would work best for my receiver. I would like to, if possible, stay under $500. I've considered the Def Tech ProSub 800 8" (300-Watt) or Def Tech ProSub 1000 10" (300-Watt) or MartinLogan Dynamo 500 10" (360-Watt). But have no working knowledge on any of them. The room itself is about 15' x 15' Any suggestions and/or experience to back it up?