I'll let someone else chime in here as well - as so far my only experience with Tubes has been the MKIV - and before that a portable hybrid (Portatube) - which I really loved and initially got me looking for a full sized tube amp.
What I can say is that IMO the MKIV is very powerful, very clean background, and with the right tubes sounds quite linear to me - but still has enough euphonic mid-range to really complement both the K701and Beyer. Mind you - unlike some who really want a wire with gain scenario, I prefer a little warmth and body to both the Beyer and AKG - while still retaining their strengths (linearity, clarity, sound stage etc). The LD is built well - and to me sounds really good. For it's price point, it should at least be a contender.
Will be interested to hear other recommendations.