Well, you just have the 160 ohms, +22dBu balanced outputs ( x 6 each) so why do you need a preamp?

Im going to use a XLR patch panel (12 in, 12 out) including an LDR level control.
Sure, It also works with a stacked rotary switch type 20-23 positions-6 wafers (one wafer for each output).

If using LDR´s I need a power supply but if using a stacked switch I dont even need a power supply.

Im going to try the LDR-approach because then I could easily add an IR-remote level control