Crossover/Equalizer help

well first:I have a pioneer 4900ib h.u. and the only way to change the sub volume from there is to change the h.u. settings is to change it to where my rear 6X9's dont work and thats the only way i can change it..if the 6X9's are on that means that i cant change the sub volume

so it was brought to my attention that i might need a crossover or equalizer(dont know the difference) or somethin to help it out
is this necessary to get one or is it just bad wiring to my h.u. or do i need something

and somebody said that one of them should be bought to keep the sub from producing bad frequencies

and also for my indoor speakers..im pretty sure its best to buy an crossover for those or whatever but i dont know what 2 look for or what to get

or if there is one product that will work for my sub and speakers issue



somebody let me know plz.and if any suggestions about certain products are giving jsut keep in mind im on a low-budget with these things.lol

 

okay well everything inside should be okay but i have a few questions about my sub
umm
the 500rms p. teknique dual voice coil.4 ohms in each
but
is it a big difference in the sound quality in running an amp at 2 ohms rather than 4?
and whats the most rms i can safely run into the sub without risking a blow out or anything

and what should i get to adjust the bass of the sub and make sure it doesnt produce bad frequencies??
i was reading from all you guys that the gain is bad to turn up more than half way and isnt much of a solution

 

ya..i think im goin to get that boss 400rms @ 2 ohm for like $90

but umm do u think it would be bad to get that profile amp you showed me at 480rms??


and guess what happen right now
those idiots at car domain called saying that it was a pricing error but that they almost missed it.lmao

 

no amps.just my whole 9 cent refund
im goin to go look on there site policy about stuff like that.see if i can try to get them anyways