Hello, and apologies for late reply.
Yes it was quite painful. Not that difficult but it requires patience and care. The soldering job is not a problem, but unscrewing and tearing the amp's PCB down is not easy.
After that you can replace the 8*330 Ohm 5W resistor, which are very poor. I chose Kiwame, they are well built, heavy and sound excellent.
I've also upgraded the 4 Wima MKP coupling caps for Audyn true copper caps (decent prices, good reports on the net). You can also choose Russian NOS paper in oil caps. Just increase the capacitance for a slightly better bass response, but beware of the space inside the chassis (some caps are huge).
You can find some tweaks and reviews on the MK VI's thread, and I'll post some photos some day.
For the improvements, unfortunately I've done the 2 tweaks at the same time, so dunno who's who.
The VI's big soundstage became bigger, more air in the stereo image, more defined and better bass. The neutrality of the circuit is still there, but everything is more natural, more defined and refined. The highs are less dry, and more detail retention. And finally there was an increase in dynamic.
It's indeed a big big improvement in sound quality, affordable, and with no drawbacks for me (the tweaks stays at your own risk). One MUST give it a try before selling the amp, or ask Sword Yang at Little Dot to build a custom MK VI+ (you just send him the parts).
And the differences in tubes are more obvious.
Edited by G600 - 4/29/14 at 11:02pm