ATC scm40 or Spendor A9

We need more information--associated equipment, room size, listening preferences and priorities, etc.

Dedicated Listening room / Acoustic treatment with rug, acoustic panel, diffusion panel.
Size room : 12 FT x 32 FT x 7 Ft (3.65 m x 9.7 m x 2.1 m)
Distance available between speaker and back wall : 1.7 FT (0.5 m)
Distance from the speaker to the listening position : 11 - 12 Ft (3.65 m)

Here my specification:

Music Server : HAP-Z1ES Sony
Preamp : Tube / Shengya / CS 6
Amplifier : Monobloc / Pure class A
Speaker Cable : Shunyata / Aeros / Stratos

What sort of speaker i can use to have the best sound :
ATC scm40 or Spendor

Not sure what your amps are capable of in terms of power or current, since you did not specify a make or model, nor can I figure from the website what specs the Spendors have. I can say that ATC speakers are among the two or three best speakers I have heard with respect to reproducing realistic dynamics, though I was listening to their powered versions of the SCM 40s. I can't speak to the Spendors, having not listened to them, though they have a reputation for being very natural, musical speakers. Hopefully others who own them can help. What do you value most in a system--musicality, dynamics? That may help you in making a decision.

I am also interested in ATC and Spendor loudspeakers among others. Hence heading out to AXPONA this year.
One thing to remember about ATC is they are seal boxed design and their efficiency is lower than average. But I have only read appreciations on these speakers. There are not much negative comments on them. Spendors do also have great reviews and their sensitivity also is higher than average.
You might want to call up acousticsounds.com and talk to one of their consultants before you make a decision.
I talked to Jay at BlueBird and he indicated that Spendor will not be represented at AXPONA, which is a disappointment for me. At the same time I had asked him for a dealer in Chicago area where I can audition those. Unfortunately 2 emails to Jay have not yet been replied. So I am guessing that Spendor sales in the US are doing pretty good and BlueBird does not feel the need to reply to individual customers :-)
Finally, a loudspeaker is the most important part of audio equation. Folks here can give you all the information. But it is you who can make a judgement after listening to them. Try to audition both, is the best advise.

Never heard ATC but was researching them awhile back and they look like the mosr overbuilt speakers I've seen. Take a look at the magnets on the midbass drivers; absolute monsters.