I looked in my inuke 3000 DSP and it does not have the same power switch as yours does. Mine is just a simple DPST switch. I just have 2 wires, both blue that go into my simple switch.
For your amp I would do a little more testing before purchasing anything. I am curious about the smaller wires going to that switch.
Does either of those small wires have power when the amp is shut down?
When the amp is on are both the red and black small wires at the same voltage?
When you are turning off the amp, does one or both of those wires still have voltage? for how long?
You probably can get by with 2 separate relays or a DPDT 12v relay, but it would help to know what is happening with those low voltage lines.