I would love the Mark V if it did not use the simul-class circuit. If this amp had full class A/B 50W it would be awesome. When I use the 45W mode, I burn though tubes to quickly (a few hours vs 6 to 8 months). Also had to replace all grid resistors since the Carbon Comp ones failed. If the Mark V sounded as nice as the RA100 or Roadster at 50W I would be very happy. Perhaps I am just not on the Class A bandwagon. The 10W mode sounds good too but seems to be the only way to get that tube saturation similar to the Roadster or RA100 using the 50W setting. I would trade in my V for a version with full Class A/B at 50W as long as the 100W mode was available. Even better if it had Dual Rectifier for use with all channels. Call it the Mark 6 or make a new product series that marries the Rectifier amp with the Mark Amp.