Really depends on the user interface for the input, what features/operations you want inside the cabin and what level of audio quality for the output.

I'm not an audio guru so I'll leave the discussion such as wiring, AMP, speaker, DSP, etc.

You can leave the OEM head unit as it is and never use it again.
Instead, install Bluetooth receiver, smart devices, etc somewhere inside the cabin.
Connect mobile phone, touch display or whatever I/F and use voice command, etc to control the source, volume, etc.

The technology is still evolving every day and there are already 1,000s of devices available.
It's up to one's creativity/idea on how to configure these to achieve one's demand.
The car manufactures, authorities, etc are looking into how to connect the car to the net in order to improve safety, traffic flow, etc and 5G is one of the early phase for this.
Thus, something achieved today could be outdated within short period.


Some owners went with Willmans head unit modifications.
If you search using the keyword ' willmans site:nsxprime.com ', you will find many examples.
One of them here; http://www.nsxprime.com/forum/showth...ment-head-unit


If your existing OEM head unit/amp/speaker are still healthy and operational, you could connect audio adaptor at the CD changer port and use the buttons/knobs of the OEM head unit to control the source, volume, play list, etc.
The popular choices are the GROM and the USA Spec devices but I think the latter one is NLA so probably GROM is the safe choice.
GROM also offers the Bluetooth receiver.

GROM example;
http://www.nsxcb.co.uk/blog.php?1811...round&tag=grom

USA Spec example but most likely NLA so just information only;
http://www.nsxcb.co.uk/blog.php?1811...d&tag=usa+spec


Above are just some examples to get ideas and you can do many things even with the current technology.
The cost and the looks are different story....


Kaz