15" is definitely too big.
funny...when i had my monte carlo, i ran a single cerwin vega 18" in a ported enclosure in the trunk with a 500W amp i borrowed from a friend. the bass was ridiculous, and i had to give the amp back after a 2 weeks, but it was fun.
the diamond audio 10" DVC looks like a good deal. i'd love to find a pair of Polk dB or dX subs in that range....
