I think if you need a head unit this is a fine way to go. I would recommend buying an actual brand name but thats just me.
If you dont need the new head unit just get a bluetooth car kit and it will do everything that you describe.
New BT car kits will be coming soon that will have the ability to play music through bluetooth. I am personally waiting for this as I have a music phone that I currently hook into my stereo by bluetooth. For this feature you would need a phone with A2DP.
I have maybe a dozen headsets, a bluetooth GPS, the bluetooth gateway for my stereo and a set of stero headsphones. Its cool stuff.
more info on Bluetooth
http://www.bluetomorrow.com/content/section/100/275/