I can't speak to the Axiom Center channels (although I do own an EP500), but in my opinion there is nothing wrong with crossing the center over at 80hz. I currently own M&K 850 speakers and they are sealed and don't go below 80hz. I like the center much better than the Polk LSiC and the Monitor Audio Silver center I previously owned and both of which went down to around 50hz. If the Axiom Center channels are designed well (and I am sure they are), I wouldn't stress about needing to cross them over any lower.