I had a pair of Belles MB-200 mono amps for a couple weeks driving a pair of Sonus Faber Amati speakers. The result was tonally coherent, no obvious peaks/valleys, not fatiguing, but overall just plain and rather boring. Not much in the way of 3D or powerful dynamics. There was no hint of some of the magical attributes that often come with tube amplifiers. The Symphonic Line RG1 amp at about 2/3 the power rating had far a more powerful presentation, bass control, dynamic contrasts, and indeed some of that tube amp magic.
I also run a pair of BAT 600SE mono amps and these bring so much more life to Sound Lab A1 speakers than the Belles and this is long before the BAT amps really start to get in their groove. The Belles is just too relaxed of a sound for me.
If you like the BAT sound, and don't need all the power of the VK-500, I would suggest getting a newer BAT model, perhaps the VK-250 or even the 255 in the SE version as the additional capacitor banks would likely make up for the reduced power rating and these later amps bring on many refinements over the 500.
