I've had my MKVI+ for three days now, and it f-ing rocks. Even with the stock tubes it's better than my former WA6 with Sophia Princess and EH 6SN7 tubes. It's powerful and it sounds amazing. Hearing balanced audio too for the first time was incredible. I finally was able to hear what everyone was raving about.
A couple of things to note:
1) The fans are a little loud. It doesn't bother me, but I can see how it would others. Replacing them with a pair of silent 80MM would be easy. Maybe some isolation cones too while the bottom cover is off.
2) I'm using them with HD650's, and currently have the gain on high. This maxes out the tolerable volume at about 70. However, there's also a very, very faint buzz on the right channel that wasn't there when the gain was on low. I'll probably set it back to low anyway. I have some ATH-W1000X's that are out getting recabled with a balanced plug. I don't think high gain with those would be good anyway.
3) With a balanced source playing, the balanced headphone output is louder than the SE headphone output. I guess this is normal?
4) With both a balanced and SE source connected, the SE source can't be heard unless the XLR cables are unplugged. Even with the balanced source turned off or with its power cord unplugged. I'm not sure if this is the amp's design, or has something to do with my balanced DAC.
Anyway, long story short, it's worth every penny. I ordered It directly from David who was very helpful and friendly. Shipping was very fast too. It left HK on Sunday 22nd and arrived here on Tuesday 24th. I ordered it on the 11th, expecting the 3-4 week turnaround, but got it in under 2 weeks.
Very anxious to hear what different tubes will sound like. Just still amazed by the stock tubes. My only comparison though were the stock tubes that came with my WA6. Those were bad. For a couple of days after getting it I was contemplating returning the amp and going back to solid state. They got a little better as time went on before the big jump to the Sophia. I was sort of expecting the same thing with the MKVI+. Nope. Tranquility right out of the box.