The HD800 and LCD2 sound much better out of the WA22, and I actually prefer my D5000s out of a modest SS amp (x-head).
But I do recommend the RA150 for the HE6 and K1000. A few other Head-fiers have liked the RA150 with the HE6, and cacatalysis actually ran his modded WA22 with the RA150 and HE6 just like I'm doing with good results. I'm sure it doesn't compare with a Darkstar but I can't say for sure because I've never heard one. I just know that it's a great match and straightens the HE6 right out in regards to the complaints I have read about them by those who haven't powered them adequately. It's a very clean, dynamic amp that is intended to power near-field monitors in a recording studio. It has RCA and balanced inputs, and is a dual-mono configuration hence the twin volume pots.
But I will say this: don't get a used RA150! If you do you will be disappointed, as they can develop some channel noise. They see heavy use in recording studios, which is its intended environment and a couple of us have had bad luck with second-hand RA150's. They're only $150-200 new though, and it's design has remained unchanged for three decades which is one of the reasons why it's such a bargain.
