To address Lizards original question "Can somneone recommend a good active crossover that I can use with both subs, a an anit-resonance filter and the ability to adjust what goes to my mains?"

I use a similar one of these from NHT. I use the X1 version since I have their speakers but the X2 version is for non NHT subs. Lots of capabilities.
http://nhthifi.com/current/products/speakers/x2.html