From my experience with the HE6 and the HE500... I would say that the HE6 and the HE500 sound somewhat similar but the bass quality on the HE6 cannot be matched by the HE500. As I compared both, and I would say that the HE500 sounds like a HE6 but something is just limiting the 500 from performing like the 6. It just doesn't dish out that final bit of performance of the 6. I would say that the HE500 is maybe about 70% of the HE6. But the HE6 is a real pain to drive and I think that is the main reason why people don't really buy it much..

The speaker amp you were referring to was on my set up from that day?