I own older Soundlabs that are TOUGH to drive. When I bought them I had a pair of pricey Lamm hybrid monoblocks. A friend was about to buy Soundlabs because he loved mine, so he trotted over one day with a KSA250 that he could purchase to drive them. Well, after about two minutes after putting in the KSA250, all jaws in the room dropped. A few hours later, I was advertising my Lamms to sell.
Ended up with a FBP300 which years later is still driving my Soundlabs much to my delight. I don't really have an opinion on post-D'Agastino Krell gear, but those older class A amps are pretty darn special. Cheers,
Spencer