The M4 won't fit in the MoCoSo case. The M2 is the only bolt-in PSU that has a chance of powering that setup. An M1 will fit in the case, but is insufficient.
TV tuners in a moving vehicle are a waste. Be prepared for craptastic reception on the TV if you decide to run with it.
If you want a volume knob, I suggest using an EQ that has a master volume knob. Using the Griffin is a good idea, but if the PC locks up with something playing at full volume, the Griffin will be useless.
USB GPS units are better only because you don't have to fiddle w/ bluetooth connections.
I doubt you'll be disappointed with the audio quality.
Get a USB hub that takes 5vDC and power it from the PSU's 5v rail. Or get these for a premium price: http://store.mp3car.com/DC_Powered_4..._p/adt-015.htm
You need one of these for all your audio inputs: http://store.mp3car.com/USB_Audio_Se..._p/aud-003.htm
The specialized cable for the HD Radio unit (you may have factored that in).
Additional wiring parts for power, audio, etc.