another option for you for the head unit would be an upper end eclipse deck...they are great sounding decks, and they have GPS built in without having to have a screen, oh yea they are sirius compatible...the cd 4000 and above have the GPS (area shot) feature available...look at their website (www.eclipse-web.com)...and audiovox makes a very nice rear view mirror replacement that has a screen built in that comes with the rear view camera for $399 at circuit city...(sorry i work there so i know all the prices way too well) this would solve all your problems minus the sub and amp...
oh and IMHO i love MBQuart and Polk Audio speakers...i think they are both great sounding speakers....the polks are a little "warmer" sounding but the MBquarts are a little clearer...
pbkid