Bonjour Peter and Franz,
Peter : It makes sense that depending on the speakers to drive, the choice of amp can vary.
Even though I prefer the 300 over the 500, I did enjoyed very much listening to Geoff Phillips's 500 with his Totem Mani 2 and later with his Kharma
BTW I'm still in contact with Geoff!
As you can see in my profile, I'm still an admirer and owner of Sonus faber speakers! As a matter of fact I have 3 pairs of Sonus faber!
Thats great, hope you are fine, still enjoying music replay through naim and your beloved Sonus Amati. So do I actually after some times of less interest I found my way back and enjoy it more so than ever. Even faced with some signs of presbysaccusis it has never sounded that good before, possibly due to DR and LP12 Upgrades.