I doubt these count as "second systems" because I'd be using the same amps/source. But though my main speakers are Thiels (3.7 and 2.7) I have a variety of speakers I also switch into the system: MBL 121 monitors, Waveform Mach MC monitors, Hales T1 monitors, Spendor 3/5s, Thiel 02s.
Yeah, I got the sickness.
My DREAM second system would use Quad ESL 57s. And in fact I was actually offered a pair free. But try as I might, I couldn't come up with a place to set them up that would work.