as far as I know the AUDYAs processor is 80 MHz
( But Tyros 1 -4 is not much faster... )
Point 2 :
Itīs a known bug, here is a workaround :
Just select the voicebank you want to assign to a variation PRIOR you select the style.
So select "Piano", then open the style, set "Grand" for Var A.
Select "Sax", open the (User ! ) style again, choose Var B and set "TenorSax". Then save. And so on for all 4 variations...
Point 4 : FIles starting with underscore are backupfiles that can be deleted !
Point 5 : Thatīs normal, because during playing styles the Audya is accessing the harddisk ( to load and play the audio-parts )
Point 1 and 3 : Maybe your harddisk is fragmented ( and / or the filesystem is damaged ).
You should connect the Audya to an Windows-PC and run "chkdsk" and "defrag". PRIOR UNPLUGGING THE AUDYA CHOOSE "UNPLUG HARDWARE" from WINDOWS, otherwise data-loss could occur !!!