I'm thinking of replacing my Klipsch KSW300,15" bass reflex tuned port,300 watt continuous into 4 ohms,25-120Hz -/+ 3db,max output 112db with a svsubwoofer 20-39pci. Will this be an upgrade of even or downgrade?
A pb12-isd/2 or pb12 plus/2 would be a major improvement. 20-39 pci is still an improvement but not so major I don't think it would WOW you. The KSW 300 is a good sub. If you have the space for two subs get the 20-39 pci and try to blend it in with the KSW 300. That would give you comparable performance to a pb12-isd/2.