Jadis JA30 - Quad ESL63 .. 4,8 or 16ohms?

Hello guys ,

I have a friend who owns a pair Quad ESL63 and he drives them with two Jadis JA30 KT88 monoblocks
He always used his JA30 with 16 ohms internal setup .. but we have read somewhere he could get better result setting his JA30 for 4 ohms
Do you agree or did you have better results with other settings?

Thanks to EveryOne for your opinions/suggestions