I e-mailed SVS and for my 16x20x9 room they recommended the 20-39+ but like most others here I want to take it one step up "just in case" so I am considering the PB2-ISD. I noticed that alot of others here take it even further and go with the PB2+. I think that may be overkill for me but I want to be sure so here are my questions for the ISD owners: What size room do you have? Have you ever bottomed out the sub? What levels do you listen to? How does the sub do with music? What do you have your sub set at, (i.e. 1/4 or 1/2 volume)? Do you wish you had gone with the PB2+? If so why? Thanks in advance.