I eventually wound up with the TG16 + CD that I had as a kid, a Turbo Duo that a friend of mine gave me about 6 years ago when he was moving because he knew I'd like it, and a PCE brief case I pieced together after getting a PCE from Black Tiger because why not?!
I can't exactly explain any way other than lawl collectard, but I enjoy having different sets of hardware. All of the NEC consoles had such interesting and generally stylish designs that I like having them around. I don't think any console has ever looked more appealing to me than the Turbo Duo. But then after I got a Duo finally, years later, that still left me wanting the Briefcase.
Currently, the only turbo games I have a doubles of is a Devil's Crush and like 3 Kieth Courages. I found a second copy for cheap and raffled it off but then the winner never messaged me. At some point I'll likely raffle it again but I'd have to not be lazy.
With other systems though, I've got a few. The only one of interest imo, is Mark of the Wolves on Dreamcast. When DC was on its way out, Fatal Fury Mark of the Wolves came out for $20. I thought the game was super awesome so I gladly bought a copy. I was at Best Buy about a month later and, lo and behold, all things DC were on clearance. I picked up 6 or 8 copies for $5 each because, well, who knows? I gave a couple away years ago but still have most of them lying somewhere in my parents attic.