what size speaker wire do I need?
 

Here is my system I will be installing soon:

Alpine 35x2 CD head unit
6.5 inch Clarion door speakers with passive crossovers
300w Alpine V-12 amp
150w Alpine V-12 amp
2 JL audio 12inch subs

The 300w amp will power the subs and the smaller amp will power the Clarions
What gauge speaker wire do I need for the subs and door speakers?
I was told 12# for the subs and 16# for the doors.

that sounds fine....just make sure you have a decent sized power wire from the amp to the battery...something like 4guage...but only if something that big fits through your door, under the hood...otherwise step up to 6 or 8...but its good to go with big for the power source