I believe only one person on this forum has had the opportunity to be able to compare those 2 subwoofers. Myrison had the PB13 and compared it to his then EP600. He now has an EP800 but no longer has the PB13, but he would be the best person to contact about his thoughts of the 2 subs.
I have also compared my PB13 with the EP600 and I felt the PB13 has more low end feel to it than the EP600, but the PB13 sounds dry in comparison with music. IIRC, Jason(myrison) stated that the EP800 has the same tactile feel as the PB13 along with that textured/rich sound Axiom has in their subs; to me this would make the EP800 the perfect sub.
