Perfect match for ATC speakers

We have a pair of ATC in the recording studio, Job amp ( out of production but rock solid reliable ) does a fine job. Mastering done on a different setup.

Have fun, enjoy those speakers….

Having used/heard almost all the ATC speakers with various amps, it is one of the most authentic sounding speakers in the world. Hence it is worth going the extra mile to give it what it needs. 

SCM 11 is one of their easiest to drive speakers. You didn't mention your budget, but here are some obvious choices at various price points

Value for money
Naim Nait 5si - Don't go by their 50 watts rating, they rock hard and don't clip easily
Nice and easyATC SIA-150 integrated amp - straightforward match and good sound
TubeRogue Stereo 100 with a good neutral preamp - More expensive but more interesting sounding too

Buy an older class A amp to drive them and you’ll be in heaven. Threshold, krell, levinson. These can be had for 3-5k. 

Try to pick up a used Anthem P2 it does not get hot and can drive any speaker that you want without clipping 325WPC @8ohms and 500WPC @4ohms
You can run this amp all day and not worry about about running out of steam, they can be had for around 2-3k used.

Missed the budget but here goes. Parasound Monos, AVA monos,
Buy more power than required so when you upgrade to something
like used 40SMTs you are set. 
Nice system by the way!