I currently have 5 systems that I listen to regularly. Each has its own character, sound stage and good/bad. Some are better for classical, some are better for jazz, and others just rock. My issue is I have not been able to find the "perfect" system for every type of music.
Also, there is a size and portability problem. Upstairs I have my "smaller" systems to make the spouse happy. In the basement, I get to spread out and have my 2 "big" systems down there for when I want to have a long listening session with a wee dram of pour. I'd hate to have to move systems every time I wanted to move to a different area of my house.
I had 6 systems, gave 2 away to family, and just picked up another yesterday. My other issue is that when I give away or sell something I miss "that sound". For example, I gave my son a pair of JBL 4312's. Missed the "JBL sound" and picked up a pair of JBL 4311's yesterday. Had a pair of Linn Kan's, sold and missed the sound for vocals, bought another pair.