Just installed my new Sony HU I got the CDX-GT710 and it is awesome...

I think I see a mp3 player jack is that right? Great jog on your installation...

Thanks lenore
Yes it is an Aux/ mp3 input jack... which is really nice to play tunes from my mp3 player the other cool thing is the way you can raise the sound stage so it sounds like your speakers are elevated and not all the way down on the floor, like before. This HU definitely improved the sound of my tunes
The next model up was the CDX-GT81 and it had a USB input along with the aux input + the 4 volt pre-outs I went the cheaper route but can't say I missed out on a lot...I hope