ATC SCM40A speakers

I had a quick listening session (about an hour) last week with the SCM40 passive. 
Liked them a lot. I haven’t heard the 803D3 in the same system but based on my experience owning B&W N803 and listening to 803D3 on multiple occasions, the ATC are more laid back, warmer and not as detailed right out of the gate. They’re engaging and natural sounding. They image very well. Takes time to begin appreciating their sound - they won’t smack you in the face with resolution.
Totally different design as well - the ATC are sealed cabinets whereas the B&Ws are ported. The passive ATC are easier to drive than the B&Ws.
I would recommend listening before buying. If you like the resolving power of the B&Ws and your system is tuned and optimized with the 803D3, expect to potentially begin making additional changes that would re-align the sonic signature to better suit the more laid back back and warmer ATCs. 
Keep in mind I’m referring to the passive version. I can’t speak to what the active ones sound like. 

Are you looking at the pair for sale on USAM?

Quite the discount off retail...

those are passives not the active version the op was looking at

Incorrect, sir.

They are the SCM40A active speakers. Retail $13,000, selling for $8000.

Less than a year old. 

This is definitely one of those situations where you must simply go out and  thoroughly audition both pairs of speakers and let your own ears be your guide.  Happy listening.