Hi Angelo,
I am over the moon with these speakers in combination with a Townshend Allegri pre and Avondaled CB250 power. Up until now my ACB250 has always been bettered by my EAR534, but not now. In this context the ACB250 wins, and this is the best SQ I have had at home; it is equally as good in AV mode!
The 534 is not bettered in all areas. For instance, in vocals: I would give the edge to the 534, and especially on less than good recordings the 534 is kinder, extracting the best and not highlighting the poor. But the sheer speed and dynamics of the ACB250 is marginally ahead of the 534, and it is more transparent.
As it happens I have an unaltered Naim CB250, through the APXO SBLs it is definitely a step down on the ACB250, whereas in other applications I had not heard this.
I thoroughly enjoyed the SBLs in MkI mode, enough to decide that these will be my last speakers, so I spent the money getting a full set of drivers from Niam and having them installed. I am VERY happy with my decision.
Your SBLs with APXO was a good buy and I look forward to your thoughts. It is absolutely worth making sure the seals are intact and they speakers are properly installed. You can buy the bits online cheaply rather than buying the expensive official sealing kit.
M