In my experience the Beseler 23CII is quite stable, more so than an Omega C760 system that I used to use.
Despite what you said in your post, I suggest that you get a Beseler 45 MXT which is quite compact for a 4x5 system (not that much bigger than a 23CII), very solid, very affordable used, and allows for future dabbling in 4x5 film.
I have a Omega D5-XL and a Beseler 67SC (which uses the 23C chassis). Both of them are bolted to the wall, as is the table I project onto. And the walls are bolted to a concrete slab. No such thing as too much enlarger stability.
The big problem as I see it is the fact that the column acts something like a tuning fork. If you have a wood floor and jump on the floor, you can probably see the enlarger shake at the top. While you're probably not going to be jumping on the floor while you're printing, the table and column will amplify vibrations.
Of course, even the house can have vibrations. When my wife lets the dog out downstairs she tends to slam the door which is on the same wall as the enlargers.
With a little bracing any enlarger can be made quite rigid.
In my experience the Beseler 23CII is quite stable, more so than an Omega C760 system that I used to use.
Despite what you said in your post, I suggest that you get a Beseler 45 MXT which is quite compact for a 4x5 system (not that much bigger than a 23CII), very solid, very affordable used, and allows for future dabbling in 4x5 film.