You can try to put them on Craig's list, but don't expect much money for them. They are pretty common, even the flip top bottles are common enough to not warrant a high price.
I like your three tier. I have one I am sketching right now that is similar. I haven't been as active brewing lately as I got an air still for Christmas. Way into that science now.Just joined the SMF yesterday, and I'm pleased to find a homebrewing thread here as well.
My wife bought me a kit over 20 years ago, and I've been brewing ever since. It didn't take me long to decide to build my own system, a tower on wheels that I can move outside to my covered patio. It's all gravity feed, with a pump for water transfer only, and an ancient Phil's/Listerman sparger. Nothing fancy; I like to keep things simple.