Susan39
I have the F040, not the F050 and I can say I love it. My guys were switched from some smaller, cheap craigslist cage finds to the F040 and I believe they thought they'd died and gone to heaven. I've never seen the F050 by comparison, but if it prevents you from getting a second cage in the future, I'd stick with the F040. In my (somewhat limited) experience, it's hard to stop yourself once you get into finches! You'll want another species at some point and will downright
need that second cage.
In regards to the shelf being so low, it works just fine for me. I keep my finches' food bowls, millet, and greens towards the bottom of their cage with their perches, greenery, and bath taking up the middle and top. This allows me to access their food dishes from the bottom door, which disturbs the shy birdies a lot less than I ever did with the smaller cages. As a result, the low shelf puts everything right where I need it. (The only thing I can say is that I've taken to just sitting on the floor as I go about refreshing their food, etc, because bending over to reach in that door was killer.)
While you're at it, look at Prevue's mesh seed catchers! I keep one of those around the base of the cage, with the food below the top of it and it has been downright wonderful. Just ordered a second, in fact, so that I can put a fresh one on the cage when I have to remove the other for cleaning. (Nothing in or around a bird cage is safe from poop!)