Do I need a sub woofer to match my ATC SCM11s

It’s very difficult to integrate sub to the system and most of the subs are awful.
The ATC SCM 11 are very good speakers you sure that you are lacking low frequency in your system ? If so I would try to upgrade all the cables including the power chords and if it’s not help only than moving to floorstanders .
I have had before sub in my system and got reed of it because the low frequencies were artificial and exaggerated.

why can't there be a right answer?  all joking aside, that's my fear with the sub: I'll never get it right and I will just add another piece that won't provide that ultimate solution that I seek. I don't want to find myself further invested in this current setup and unsatisfied.

Hi Itzhak1969, that's my fear exactly. I am using my stock power cable and I'm currently arranging to have it upgraded. how much of a difference can that make?

My limited audition with passive ATC home monitors (SCM 19s?) at last year’s Capital Audio Fest also left me with the initial impression of sounding "thin" in comparison to other similar rooms there. It left me wanting another audition to get my arms around those particular speakers better in that they appear to be of very high quality in terms of construction and design. It’s one of those audio mysteries to me at present that my curiosity won’t let go.

Upmarket power chords can make huge difference also interconnects and speaker cables but you have to match them carefully to your system ,if it doesn't help and you feel that your speakers are not good enough in low frequencies it's better to upgrade to floorstanders than adding a sub to your system, I in general not a big fan of standmount speakers they can be very good at transparency, image and clarity but lack in dynamics and low frequencies.