Qualitatively, the Rag is better then HDVA600 for a variety of reasons. The Rag has much lower output impedance, although you may find the softer more laid back sound of the higher impedance HDVA600 more palatable. I like the HDVA600 very much for the HD800, but didn't think it drove a mid-level HFM, i.e. HE-500 very well. One other concern with HDVA600 is that the amp tended to strongly impart its signature regardless of what DAC I plugged into it. Shoot, I mean it almost sounded the same with a iPhone 5 as with other more capable DACs with the only major difference being compressed soundstage of the iPhone. But again, this could be a good thing. The Rag has much better at slam, microdetail, and dynamic contrast - but this could also be a bad thing. The Rag with a poor quality source does not sound good at all; but that's me talking and I'm kind of a nutjob when it comes to sources.