I've seen some listings of people who are selling 2nd hand 12" Targas with an enclosure. You can get a 12" Targa and a box for less than 3k. Try mo sa Kotseaudioclub and check out their classifieds for car audio equipment.

Since you have a charade, i'm not sure if a big box will fit in your trunk..unless you are willing to sacrifice your trunk space talaga. Do you want boom boom sounds talaga? or are you into more sound quality? You'll probably want a 4 channel amp also, try mo Thunder Audio 4 channels 100watts rms each. bridge channels 1 and 2 for your speakers, 3&4 for your sub. Cost almost the same as V12 amps. But with you budget, you can easily fit a full system in, without the headunit. Go all Targa hehehe. Bang for the buck talaga. Plus you get lifetime warranty. I'm using All Targa as well.