humming from sub

thats probly true haem. lets just say i am putting together pieces i have laying around to put in my dads truck so the simpler the better as long as it gets the job done. if you know of anything, or a couple, i will look into them.

dyohn, my deck is a sony cdx ca810x

OK, that's an older head unit and it has 2-volt pre-outs.  So, most likely the Lanzar amp can handle it.  Which brings us back to the ground loop issue.  Try this for grins: make sure all three pieces 9head unit, crossover, amp) have ground connected directly to the car's chassis.  Do not use the factory wiring harness ground for the head unit.  See if this helps.  If no difference, try directly grounding the outer shield of the RCA cables at the amp.  Do this by taking a small wire (18 gage or smaller is fine) and connecting one end to a good ground.  Take the other and touch it to the outer part of the RCA connector.  You may have to back the cable out a bit to expose the metal outer ring.  If this solves the problem, then you can either permanently install your ground jumper, or you could try connecting a wire from teh crossover outer case to the amp outer case, as sometimes this will do the trick. 

Also, since all three components are, franly, at the VERY LOW end of the quality spectrum, it might simply be that they don't play well together or are simply worn out.

Cheers and good luck.