is equal to what retail subs on the market ? I'm currently in the works of building a DIY Tempest sub using Adires reference SBB4 design found here: http://www.adireaudio.com/Files/Vent...plications.PDF My amp will be a Kenwood 125 watt per channel reciever (using both channels to power the Tempest). I plan on upgrading to a Behringer EP1500 in the future. I was just curious to see what this sub will be comparable to on the retail market. Thanks for any input you guys give .