I personally own the bel canto ref 500 S. I love the tight bass and sub low frequencies they present great micro detail. Though it’s a really picky amp imo. I went through two different tube pre amps, and tried about 4 different power cords.
I found the bel canto and the LTA microzotl preamp pair best together. That’s what’s playing in the background as I’m writing this post.
As someone mentioned Pass Labs. I’ll be receiving the xa25 in about two weeks. Two completely different presentations. Though the contrast will be an interesting study.
I once heard that bel canto amps need a year to break in. Though after using this amp off and on for about a year it comes into its own. I’d definitely say the ref 600 m used market would be a real treat.
They really need time to open up. They sounded grey and a bit bright for quite sometime. You’ll definitely need a tube pre for optimal sound.
Hope this info helps.
My best