For those of you out there with planars and wanting to try a full tube setup for amplification, I acquired just a few days ago a great deal locally on an MP-301 Mk3, and I was a little bit worried about whether the amp would effectively drive my HE- 32 ohm set. I can report happily that this amp can drive them with no sweat Even using the "standard" default 6L6 driver tubes (recommended for headphones), I can hear almost zero hum (a complaint on earlier versions), and the sound is great. With CD player as direct source, I can barely go past 10am on the volume before the music is too loud on most CDs. Midrange heaven and sparkly highs. This amp IMO is a very well-built beast of kit for a low price. It absolutely dwarfs my LD1+ (I'm not criticizing the LD1+ at all - I love it with the GE JAN 5654W tubes). Love the black glossy paint finishing as well. Would look great on anyone's hifi equipment shelves. In terms of driving full size speakers, this amp easily drives my Tekton open baffles OB4.5 (92db efficiency, 4 ohm). Again with CD as source, I don't go beyond 11am on the volume -- very loud room-filling tube sound with power to spare. Anyway, just wanted to let folks know that the MP-301 Mk3 is a really well-built, great sounding amp, versatile, and very capable, with a huge choice of tubes available for tweaking the sound. I don't have any 600 ohm sets so I can't speak to how well it would drive those, but I can't imagine the MP-301 Mk3 would have any problems.