Help with Crossovers

[NextGen]

I installed a Pioneer Z1 into my X. Next year I plan on upgrading the rest of the sound system. I want to get an aftermarket amp to power the door and dash speakers. I was thinking of getting a 4 channel amp and then using one of these crossovers to split the signal to the speakers, http://www.audiopipe.co.uk/Productlist.aspx?ChildID=25.

I was thinking of using the CR-3003 for the front speakers and the CR-2002 for the rear. These are for sale on ebay and display a different frequency range for some of the connections (in parathesis below).

CR-2002
Tweeter - 20KHz - 3.5KHz (ebay 4.5kHz)
Midrange - 3.5KHz - 500HZ

CR-2003
Tweeter - 20KHz - 4.5KHz (ebay 3KHz)
Midrange - 3.5KHz - 500Hz
Woofer - 700Hz - 20Hz

1. Is this a good or bad idea?
2. Does anyone know if these are quality crossovers? If not can you recommend better?
3. Is it bad using different crossovers for front and rear?
4. Would I be better off using CR-2003 for front and rear and then leave the midrange unconnect for the rear speakers? Is it okay to leave a connection unused (no impact on ohms or anything like that)?

Sorry for so many questions, I am a noob when it comes to crossovers!