Atlantic Technology SP-8000 inline with REL R-218 sub

I just recently found a Atlantic Technology SP-8000 to be use inline with my REL R-218 sub. This made a day and night difference not just flexibility but also better gain structure. I always felt REL, I am not sure if every other different model have this issue having weak or inadequate gain for a particular  level. My HSU STF-2 never had this issue wither it was ported. My REL gain was setting near max level and I couldn’t get enough "punch" if you really want to call it that. Yes it is so far the most musical sub I heard so far but being a sealed sub it should still be impactful. The SP-8000 fixed a few flaws I see in the rel. Ref level,  frequency  Q adjustment,  and most important, enough gain now.  

One more thing to add to this was that yes I tried speakon high level connection and was still getting inadequate level. BTW, I have low level input in the .1