Technically I don’t have a 2nd system running in concurrent mode or in two separate rooms. The reason is simple: I have got a nice sound treated room for dedicated audio and video viewing. It is hard to find another space in the house to do proper sound treatment for the 2nd system.
Having said that, I do have 3 pairs of speakers (B&W 705 S2, Herbath C7ES, B&W 702S2) and 4 units of amplifiers in rotation every few month (Hegel H20, McIntosh MHA 150, Benchmark AHB 2, and Parasound Halo A23+). After many years in this hobby, I have paid enough tuition to learn that you can never have a perfect system for every types of music you hear, so mix / match and rotations are fun and necessary :)
I do keep the upstream components fairly stable (Technics 1200 turntable, Rotel CD player, Hi Fi Rose network streamer, Gustard & Denafrips DACs feeding into PS audio BHK preamplifier).