running 2 hifonics xi zeus's...

how should i go about doing this ? i currently am using y adapters but i have noticed that if i use the lpf on both of them, the closer i get to them being matched they start to cancel out. like theres no bass at all... but when i use the lpf on my hu i dont have a problem. only reason i want to use the lpf on the amps is so i can use my epicenter and i can run my lpf lower on tha amps vs tha hu.

any help is greatly appreciated.

BaSs.