Audio Pro B2-50 Subwoofer Anyone?

I realize that Audio Pro has not distributed in USA for over a decade, so this thread may be aimed at the Europeans. My Audio Pro B2-50 has served me well since I purchased it in about 1987. It has supplemented my previous speakers which lacked the bass I needed in the 70 Hz and down registers (Dahlquist DQ-10, Quad ESL 63, Tyler Woodmere 2- to a lesser extent). My new Tyler full-sized Woodmere speakers solidly go down to the upper 20 Hz region, so the sub is currently dialed in to crossover at 30 Hz, the lowest setting on the dial. Question: for 30 Hz and down, what difference would I notice between my aging Audio Pro sub and one of the newer models, such as JL Fathom F113? At this frequency, my music application is strictly classical/ heavy orchestral. Thanks to anyone who gives me some idea.