choose a DAC to complete my system

acoustic zen silver reference ii XLR interconnect
Cardas Clear speaker cable
wireworld platinum usb cable
Focal Electra 1038 be II
Pass labs X350.5
Pass labs Xp10 pre
Oppo BDP-105
PC computer

i'm not happy about the sound i'm getting
i'm not sure why.
maybe it's better to replace the PRE ?
maybe to get Apple computer to replace the PC?

for DAC i though about one of those:
Luxman DA-06 (Japan model cost $3000 but i don't know if it will work in the US? Japan using 100V
Meitner Audio MA-1 , found 6 month old.

or other models?

Thanks