The good news is your 75 has standard ISO connections which makes fitting an aftermarket head unit easy.
I'd advise sticking with a decent well known brand and avoid fitting any random Chinese thing to ensure you get a good quality unit and one where you can easily source a Connects2 adaptor for your steering wheel controls.
I have a Kenwood CD head unit in my 75 with rear USB and aux connections. It has a variable colour display so it can be colour matched to the interior illumination. It's a few years old so no DAB however.
