Option 1. Why put more stuff in the audio chain that isn't required? The DAC in the Marantz is supposed to be very good. I had a 6004. All DACs/filters these days in enthusiast gear are practically flawless. I wouldn't sweat it.

Either the Marantz or PC to HA1 gives you the option to do headphones only without the NAD. It's nice to have options. smile