i dont think all models have difference in HUs.
there are different type of outputs (total 4 ch = 2 preouts ) , which cannot be called as preouts... they are just wires. (at least i know for my [basic] and nicks [SX] model). we both purchased converter to covert those just wire 4 channels into preouts to connect it with amp.
and with even 2 preouts you can connect one 4 ch amp ... unless you divide channels and loose performance.
I have no idea if they have provided real preouts in SX O.
there are different type of outputs (total 4 ch = 2 preouts ) , which cannot be called as preouts... they are just wires. (at least i know for my [basic] and nicks [SX] model). we both purchased converter to covert those just wire 4 channels into preouts to connect it with amp.
and with even 2 preouts you can connect one 4 ch amp ... unless you divide channels and loose performance.
I have no idea if they have provided real preouts in SX O.