These issues have been addressed several times on the forum. Here is a summary based on my own XD9 experiences... and for the most part, observed by others.

Sound and individual voice quality outstanding. IMO, nobody touches Ketron in this area (BTW, no "muffled" sound thru my speakers).

Unfortunately, reliability is the MAJOR fly in the ointment. My XD9 is in the repair shop now. If Ketron wants to embrace the professional musician, the OS reliability issue must be improved.

On the positive side, customer service seems to be excellent.

HD is very useful and should be in every middle - upper end AK.

Glenn