SR-007, I haven't had the chance to try but SR-009 driven by a BH, I did listen quite a bit at the recent CA meet. IMO, HE500 has no chance in this fight but it's not a fair comparison in this case, of course. I still drool every time I remember the sound of that wicked combo.
maybe no chance against stax
but with TOTL amps, the HE-500 holds its own against the Abyss though, and in many ways, outperforms it