We just tested the MC-10L and the VK-2100 with a 683 pair, an RTi A7 pair and an RTi A3 pair in AVShop's demo room. These are great integrated amps for the price. Thanks Marc for inviting me over, and thanks James for your time and effort. Sa uulitin.
The MC-10L PP actually reminded me of a popular EL34 amp, minus the remote control. It sounded sweet without losing linearity or curtailing the frequency range. This amp performed great with the A3, but was also quite good with the A7. It lacked the lowest frequencies with the A3, but I found that combination better than having to live with loose lows from the FS speaks (especially with the 683). The MC-10L is an excellent choice for smooth vocals and downtempo jazz.
The VK-2100 Hybrid had the drive to control the A7 and the 683, so it was a natural for floorstanders (given their room size). It delivered a sharper sense of bite and precision, but wasn't nearly as sweet as the MC-10L. It can be quite dynamic (surprising for 85wpc), and was great with rock and r & b.
I didn't get to test them with classical works, but they're both excellent purchases. One is not better than the other, merely different.