I'm thinking about getting the Alpine KTP-445 and putting in four Kenwood KFC-P509PS components in the doors of my explorer. I read that the KTP-445 has a switch that is only high pass or low pass. So would that mean that I wouldn't get proper mids on the drivers if I had it to high pass? Or would it work fine?

 

Lo pass - 80hz and down
High pass - above 80hz usually selectable to 300hz

For your info a standard bass guitar's lowest note 40hz
standard guitar 80hz - 800hz

Switching it to highpass will cut all the frequencies below whatever it is set to

I can't see you having any problems

 

Interested in some other options at all?

 

I was gonna get a normal 4-channel amp but but the time I get the wiring and what not this option will be cheaper. Although I am not set on the components...

 

The lets find you a deal on some components then. The add on amp option looks like a great way for you to go.

 

Any suggestions for something around 45w RMS?

 

the powerpack has a "high gain" / "low gain" option.