Autoteck and crossovers?

I've tried searching the forms but haven't found exactly what I'm looking for.

I have an Autoteck SM4-1000 and SM2-1000, Kicker 07CVR124 and eight Polk Db651's (4 interior / 4 tower) and had a few questions.

On the back of the amps it has crossover switches built in, do I need additional crossovers? I'd like to control the interior, base, and tower volume separately. Any recommendations on how to do this? Would I need a third amp to make it work?

most amp crossovers just allow certain frequencies to pass thru. Generally the ones built into amps are simply high pass (high's/mids) and low pass (subwoofer). For example if you have a system with a subwoofer and full-range speakers then the amp for the sub would be set to low-pass so it did not get muddied with higher frequencies it isn't designed to reproduce and vise-versa for the full-range. Set the sub amp to low-pass and your other amp to high-pass. I personally like to have my tower-speakers run only the higher range and leave out the bass so they can be run louder without distorting. Each speaker should have their own built in cross-over sending the highs to the tweeter and the mids to the woofer. Depending on your headunit and how you hook everything up you could do all you want without adding an EQ. However the wetsounds EQ comes highly recommended on the board and will give you more control. If you don't want to put more money into the system and your headunit has 3 sets of pre-outs then you could hook it up as follows: Sub to the sub pre-out giving you control of the sub volume, tower speakers to the front preout and cabin speaker to the rear preout then use the fade to turn up either one independently (its not the best way but will suffice). This all assumes your 4-ch amp can run the tower and cabin speakers, if not then a 3 amp would be required, but could still be run the same as above.

Thanks Clotus for the tips. One more question... how do you go about hooking speakers up in parallel in a professional manner? Do you use some kind of terminal block?

That I do not know. Hopefully someone with some knowledge with jump in here before the Thursday shutdown. Also there are stereo specific forums you can check out. Those guys sure know their stuff. Its the same in a car as in boat (for the most part)

Is there a need for an external crossover when all my amps have a built in crossover switch already and i'm using a Clarion EQS746 equalizer?