This thread may prove a useful resource to others, so I'll add my 2 cents...
I have upgraded from Martin Logan Classic 9 to Impression 11A. The rest of the system consists of an Audio Analogue Maestro Anniversary integrated amplifier, cheap Cambridge D300 CD player (to be upgraded later on)...
@JohnWarren: Any more updates on this? I've also found a non-burned in pair of Impressions 11A thin in the mids and a bit dry in the bass with a relative lack of drive, energy, punch and I'm wondering to what degree is this character due to the lack of burn in. Thank you!