Single Sub. need help picking one out

I'm looking to put a sub in my g/f's car. i want it to be as loud as possible. im open to suggestions on how to tune the box and model of sub. here are the requirements:must have a final ohm load of 4 ohm300-500w rmsatleast a 12" or 15"MUST BE UNDER $100 SHIPPED (NEW OR USED)any help is greatly appreciated. I've been looking around for some time now, and cannot decide. It's going to be in a 98 Ford Escort ZX2. Thanx!

Well if you can come up with another $50 I know one that would work perfectly.  It is the Adire Audio Tempest.  Put it in a 4.5 cubic foot ported enclosure and you should be close to 150 dB's with that setup. 

Oh, forgot to provide a link: http://www.adireaudio.com/mobile_audio/drivers/tempest.htm

Steven Kephart wrote: Well if you can come up with another $50 I know one that would work perfectly.  It is the Adire Audio Tempest.  Put it in a 4.5 cubic foot ported enclosure and you should be close to 150 dB's with that setup.

Wow! that sounds really good. thanx for the tip. unfortunately, i really cannot go over $100. i was hoping to stay a bit lower than $100. i was looking into getting an older Kicker CompVR15 for about $50 shipped. any other opinions?

 :D Thanx for the help. I went with an aluminum TC Sounds D2 sub. Seems awesome, especially the price. Thanx Stephen!  :)