Power Supply:
You may wire it for 240V; in Belgium there will probalby be 230V, as it
is in most European countries. If it is wired for 220V and it receives
230 it has a little more margin, which has to be disspiated inside the
(linear) regulators. On the other hand if you wire it for 240V and it
gets 230 only it has less margin (and thus less thermal stress) but the
possibility of AC hum is (slightly) larger. It depends. The AC mains
is specified and guaranteed to be +10/-15% of the nominal value; that is
195 .. 253V @230V nominal. The power supply should work in the range
187 .. 242V when set to 220V and getting 220V or
204 .. 264V when set to 240V and getting 240V
If it is set for 220V and you give it 230V (with tolerances) it behaves
as if the tolerances were -11/+15%. When set to 240V the tolerances are
-18/+5%. So there is not much difference and under normal circumstances
either case would work without problems. So, I would just leave it.