Give these guys a call, and they will walk you thru within your budget. If you plan on doing your own install - they are very helpfull too!
http://www.crutchfield.com
Someone/Member just posted a photo of their iPod setup recently (Sky Blue Speedy)
Speakers mounted under dash. You could place a high powered 4chn amp under the boot and add a SubWof behind the area called a backseat too.
Use the forums search tool for "stereo" you will see lots of suggestions and ideas before you decide which way to go.