I successfully fitted a Sony XAV-AX1000 to my MX-5 NC. I fitted it in conjunction with the Bose factory Amp. I needed to add in a line Level Converter (LLC) between the head unit and Bose Amp. I chose this method in order to run all the original speakers. Without the LLC there is loud and extra loud...

So how did you get on with this? Did you get it going satisfactory with the Dose amp? Did you end up using a line level converter?