I never said the BH makes the O2 more forward and dynamic if that's what you mean? Dynamics has nothing to do with how forward or relaxed something sounds. Maybe the BH makes the 404Le less forward by giving it more spatial resolution- it definitely does this moving from a Pro bias transformer box with the O2 to the BH. But I haven't heard the LE on a pro bias transformer box. 
 
We'll have to disagree with the Lambda sound signatures. The regular 404 didn't have particularly hard hitting bass when I owned them. The Pros certainly did on the same amp with more midbass. The 404 did have better extension, but moot really. 
 
I'd like to hear all three now that I have a Blue Hawaii, I somehow doubt my ranking would change much from SR-404LE > SR-Lambda > SR-Lambda Sig > 404 > Sr-Lambda Pro