Hello everyone. I am thinking of upgrading my M&K MX100 sub to either the HSU VTF3R or SVS PB2 ISD (more like down grade since I paid around $1300 for the M&K a few years back) My room is about 2500sf. I am running 2 Klipsch KLF30 fronts, KLF-C7 center and Polks FX500 surrounds. I watch movie about 80% of the time on the system. My questions are: will I gain any thing by doing the upgrade? The VTF3R is cheaper and looks better than the PB2 ISD. I think the PB2 ISD will give me more output but not as musical as the VTF3R. Please correct me if I am wrong. Should I stay with what I have or should I do the upgrade and which sub should I go with. Thanks all.