The functional cone area of the 8x5 is not nearly as much as a conventional 410, which will crush the pjb handily in terms of volume. IME a PJB 4x5 is equal to an inefficient 110. I love the pjb tone and have gone as far as 3 4x5xt cabs with an 800 watt head-to get less volume than a single 212 :-(
The PJB 9B sounded amazing with 800 watts into it (Carvin BX1200), but was nowhere near as loud as an Epi 410 with a 500 watt LM2