Not my Dmax, but I put some new Kenwood Excelon speakers in our 930 Fendt along with an Excelon amp feeding a JL 10" sub behind the seat. I put an Excelon x798 in for a head unit a little while back and really like it. The only other thing I might try is a wires marine remote mounted to the armrest. It's a little tough to adjust the radio when you are going across a field, Fendt doesn't give you anything to brace your hand on like other OEMs. The Kenwood wireless remote is kind of finicky which is why I want to give the hardwired remote a try.
I'll snap some pics tomorrow when I get the amp wiring all tidied up, mount the amp and sub box and put the interior back together.
It sounds amazing though, tested it out with a lot of Primus, Tool and some RHCP.
Do have this Snapchat I took of the speakers. Previously there were no speakers in here, the headliner is molded for them though as it is a factory option to get 4 speakers instead of two. Just had to drill the holes. Ran into some clearance issues with the one, it was almost too deep and the magnet kept wanting to stick to the ROPS.
Factory Pana-pacific radio and factory front speakers which are pretty impressive for just being 4-5" speakers. The little box next to radio is Bluetooth mic.
For those who can't figure out what a Fendt is lol.