I'm not too impressed with those kennedy "middle" boxes. For the price they sell for they are not very sturdy. Only reason I have one is because I got it super cheap, like new. It works OK for small cutting tools, but the drawers are a bit flimsy for their size. There is no way I would pay full retail price for one, even if I could afford it. There are a few other companies that make a similar sized cabinet but the kennedy is by far the most affordable in that size/layout. I'm the opposite of you I like an inclosed or at least surrounded top compartment.
One option, although it might end up being too tall is to stack another bottom box on top of the one you currently have, casters removed of course. If you do get one of those kennedy boxes, I would highly suggest you spring for the ball bearing version. Maybe you could find a nice top box you like and then put a side shelf on your bottom box for a work surface.
