I had a Mk VI in my system for a while and it ran flawlessly and sounded great. I just needed more power for my speakers. This list is posted on the Pearl Audio website and you might find it useful:
Here are some new things on the current MKVI:
• High Speed Sentry Monitor circuit will shut the amp off if speaker wires are shorted or there is a gross impedance mismatch to the connected loudspeakers.
• High Speed Sentry Monitor Circuit will indicate a failed output tube by illuminating the three small tubes Red in front of the defective pair of output tubes, greatly simplifying maintenance.
• Small tube illumination for amplifier operational status indication. The three modes are sequential: Amber on warm up, Green when amp is ready for operation, and Red if an output tube fails.
• A stereo power control cable combined with a McIntosh preamplifier allows for the small tube illumination to be turned on or off using the meter light control trim function in the preamplifier.
• Power control input and output allows one button on-off operation from the preamplifier when used in an all McIntosh system.
• High Power Mono operation, MC275 has been designed for 150 watt mono use and comes with the jumper strap to connect the two channels together for mono parallel operation into 2, 4 or 8 ohms.
• Auto Off switch allows control of the new Power Save Circuitry which will switch the amplifier to Standby Mode approximately 30 minutes after there has been an absence of an audio signal.
• New Style Patented McIntosh speaker binding posts produce the very best connection with all speaker wire types and terminations.
• Higher Audio Performance Achieved. There were many subtle changes in circuits, and component values that were relatively unnoticeable by themselves, but totaled up to significantly improved performance.
Here are some new things on the current MKVI:
• High Speed Sentry Monitor circuit will shut the amp off if speaker wires are shorted or there is a gross impedance mismatch to the connected loudspeakers.
• High Speed Sentry Monitor Circuit will indicate a failed output tube by illuminating the three small tubes Red in front of the defective pair of output tubes, greatly simplifying maintenance.
• Small tube illumination for amplifier operational status indication. The three modes are sequential: Amber on warm up, Green when amp is ready for operation, and Red if an output tube fails.
• A stereo power control cable combined with a McIntosh preamplifier allows for the small tube illumination to be turned on or off using the meter light control trim function in the preamplifier.
• Power control input and output allows one button on-off operation from the preamplifier when used in an all McIntosh system.
• High Power Mono operation, MC275 has been designed for 150 watt mono use and comes with the jumper strap to connect the two channels together for mono parallel operation into 2, 4 or 8 ohms.
• Auto Off switch allows control of the new Power Save Circuitry which will switch the amplifier to Standby Mode approximately 30 minutes after there has been an absence of an audio signal.
• New Style Patented McIntosh speaker binding posts produce the very best connection with all speaker wire types and terminations.
• Higher Audio Performance Achieved. There were many subtle changes in circuits, and component values that were relatively unnoticeable by themselves, but totaled up to significantly improved performance.