120V or 240V

I agree with Kurt tank......
Something else to think about, after market power cords. You can not use a standard NEMA 5-15R or a 5-20R 120 V receptacle on a 240V branch circuit.

If you are in USA, I recommend getting it set for 120V. This will make resale (which imo, is smart to consider) much much easier. I know of some real great amp deals at the moment, but they are "shelf-huggers" due to the fact that they are 220V models. If the were only 120, they would have sold in a day.
I see no sonic benefit to a SS state amp running on 220, since the voltage must be stepped down to the same voltage for the boards,(the 220 amp has the same everything except the transformer) so it does not really matter what the line V is.

PS. How do you know about SL ? How would you rank them with other brands that are better known in the US ?

I have a local dealer that can get that brand, but with no floor samples, I would never take a chance but I almost did.

240V will sound better

"240V will sound better"

Can you give any physics reason why?
The amp circuits require the same voltages and do not know how many turns are in the primary transformer. 240 will require a larger step down (higher turns ratio) than 120.(Isn't an amp really running on 5 or 12V?) I don't see how this would change any performace specs of the amp. I could see 240 being better on a tube amp, because the voltage needs to be stepped up, but on SS the voltage needs to be stepped down.