What's your chain and tubes used in your BA again?  We've done the same test many times in the past w/ the O2 and BA and clearly not the differences.  Either there is a choke in the chain, discrepancy in our methodologies or different metrics being used.  If all you listen for is aberrations/discrepancies in FR then I could see how you could come to that conclusion.

I dunno how that could happen, i.e. O2 sounding the same or similar to the BA. I even took AudioDYNA's blind test with the Loupes and WA5 (using the TH900) and easily passed it.

Oh, I don't mean to suggest that they sound the same since it wasn't really a fair comparison (besides not being level-matched and properly controlled, the conditions were less-than-ideal). I wouldn't want to step into a strawman argument, but I'll clarify that quote is expressly in response to the prevailing sentiment that the HD 800's performance volatility is derived from aspects of its tonal balance (be it bass deficiency or treble emphasis).

Even in stock form with a relatively modest upstream (provided no issues with damping factor) I consider the HD 800's bass to be exemplary. I've never not had issues with the HD 800's treble, be it from the O2 or the ECBA.