I'll be trying out the HDVA 600 next week, using a dcs Puccini cd player as source and HD800 'phones (balanced connection). I had tried the HDVD 800 (same dcs source - *not* the built in dac in the HDVD 800) using the phones single ended (ie, jack plug into the amp). I was comparing it to the Lehman Linear amp. At the time, I thought the Sennheiser was rather cold and clinical sounding. But when I returned to the Lehman it seemed crude compared to what I had just heard with the Sennheiser. So I was disatisfied with both!
The universal opinion on the HDVD 800 thread is that headphones connected balanced, using the 4 pin XLR socket on the amp, sound much better than single ended. This is one of the reasons I'm trying again next week with the HDVA 600.
By the way, In February I asked the UK distributer what the Lehman Special Edition is like compared to the standard amp. He didn't exactly sing its praises, he just said "different". The price increase for what appears to be a change of capacitors, and an upgrade to a few inches of internal cabling, seems excessive to me.