I got a pair of 860.1 monoblocks a while ago and I'm very satisfied so far. What I particularly like about them, are the endless possibilities of tweaking their sound. You can switch tubes (KT88, EL34, 6550), you can switch between triode and pentode mode and invoke a contour switch, which provides various degrees of feedback. Plus, when you don't use the volume pot as attenuator, it does an excellent job as noise pot.
The amp came originally with KT88 tubes, which provided deep, powerful and well defined bass in comparison to my BAT VK-60. Also, the air-around-the-instruments feeling was a bit better with the Granite Audio amps. On the other hand, the 860.1 with the KT88 sounded a tad dark and didn't have the sweet midrange of the BAT. When I switched to EL34 (Electroharmonix), the sound was very similar to the VK-60, regaining that midrange magic I was missing without loosing too much of the bass definition.
The amp came originally with KT88 tubes, which provided deep, powerful and well defined bass in comparison to my BAT VK-60. Also, the air-around-the-instruments feeling was a bit better with the Granite Audio amps. On the other hand, the 860.1 with the KT88 sounded a tad dark and didn't have the sweet midrange of the BAT. When I switched to EL34 (Electroharmonix), the sound was very similar to the VK-60, regaining that midrange magic I was missing without loosing too much of the bass definition.