Hello GB, I somewhat know what you are talking about. I dont know if this will help you at all but I can give you my experinace. I have an Outlaw EX that does excellent in the LF as it does well in the mids too BUT... the PA-150 sub I have starts to overtake the mid to upper LF I have noticed. They are two differnace subs thats for sure but for my situation its works out great. I have played around with the cross overs a bit as Stitch has mentioned as I found 80 seems to be the best... for me anyhow. I also have some large Klipsch KG 5.5's up front to contend with as well, they have dual 10" drivers.
As I had mentioned I dont know if this will help but I do know what you are talking about.