One of my first cameras was the MX. Very solid and very reliable. I'm trying to buy it back from the guy who bought it from my brother who in turn bought it from me.
I doubt you could go wrong with any of the cameras that you've mentioned.
I rarely use the DOF preview. And these days I shoot mostly with a RF, so DOF preview is moot. When I did use it, I strugged to see anything in the darkened viewfinder.