So after the HU and double din facia had sat in my walk in robe for 15 months I finally had it installed into my car and I must admit it was worth the wait.
Simon from SJS installations in Frankston came out and installed my HU including handsfree and SW controlls for only $140. I supplied him various links that detailed the pin outs for the 20 pin din plug and the 14 pin audio connector and he just smashed it out of the park!
The HU I bought was a Kenwood DDX 4016BT ($270 from JB hifi) http://www.kenwood.com/au/car/visual_navigation/ddx4016bt/. It comes with a loom that allows you to directly connect to the OEM steering wheel controls so no need to buy a separate steering wheel control interface.
I bought the facia off ebay for around $160 and an antenna adaptor from autobarn https://www.autobarn.com.au/aerpro-nissan-d-diversity-lead-ap348a for $15.
Simon cut off the mating connectors from the old McIntosh unit and turned them into adaptors for the new unit. Kept the McIntosh amp and original speakers.
Before
After
I highly recommend Simon for your own installs.