I have Pi-4's but with the eminence Kilomax woofers/2002 compressionI use a Crest CA-6 with great results - 400w/channel @8ohm - the kilomax need gobs of power(1000 would work too) - I did have Classe DR-9(150w per) but not enough juice.
if you get a CA-6 - get an older one - I forget what year this model went downhill after the company got bought out.