CD/MP3 changer



I've just bought an '08 GT AWD with Bose audio and moonroof. I have two questions for you (this is a US model question)

1. Has anyone of you have gotten the MP3 changer (NOT std CD changer but MP3)? I thought it's possible as an option, no? Can I retrofit this, is this compatible with the Bose? I've seen them being sold for $400 online

2. The Bose really sucks when it comes to bass, the reason I got it is mainly for the moonroof, the two are inseparable. I'll not suggest anybody to get the Bose. However, has anyone fit an extra subwoofer to add to the bass, I don't need earth shaking sub, just more bass? How difficult it is? I assume the Bose comes with extra amp power that can be used.