I purchased the standard MKIII since it is my first tube amp and I wanted to try one out to see if all the hype was true. I have a couple of solid state amps and three different DAPs and listen only to FLAC or FLAC HD music via planar magnetic cans so I have some music experience and consider listening to music a primary activity. I have to say that I AM impressed with this little amp. Not sure if it's purely the tubes or partially the class A amplification but the sound IS very smooth and musical, more so than my other amps. There may be some coloring going on but if so it's very enjoyable. All details and depth are at least as good as or better than my solid state amps but with the overall sound being somehow smoother and more musical.
My only con so far is that tubes DO get hot and will burn you if you touch them accidentally :-)
FreedWNo, the 400i works fine though audible distortion does kick in at higher volumes using stock power tubes. Upgrading to 6n30pi tubes cures this (you need a later revision LD motherboard to use these).
As an aside, the hybrid LD 1+ works really well with the 400i too.