I used to have a pair of ATC scm19's and used them with/without a REL Strata 5 sub.
I used them with a Krell Kav300i and also a Chapter audio Preface+ and couplet pairing.
I listen to all types of music, but mainly electronic, especially Aphex twin, which might be along the lines of Dubstep.
As Ben mentioned, ATC's are very faithful to the recording, and don't hype the bass like many other loudspeakers, but they recreate the recording with absolute precision, making even the most complex music make sense.
Adding a sub to the scm19's will make a great combination, but the sub will need to be a good one. Think of the Rel Strata 5 as a minimum. A sealed sub will also be best in order to have the right character of bass to suit the scm19's.
ATC's C1 sub would be a good match, or even better, two C1's