It seems that if you hook up the HD radio module that the module takes over for the internal radio in the Z. Is that what happens? I am worried that the analog FM tuner is not as good as what is inside the Z.

Has anyone got any experience with this?

i wasn't even aware you could hook up hd radio on the z series

No, it just shows up as an external device.

This is the response I got today from Pioneer customer service:

Thank you for contacting Pioneer Electronics, Inc.

You can connect the current HD radio tuners to the Z-series.

The GEX-P10HD or the GEX-P20HD.

Use an antenna splitter and keep the analog features of the internal radio. Then use the digital radio by itself through an EXT button. Get the 20 series though...the 10 series has some drawbacks that the 20 series doesn't.