One of those little Clausing knee mills would be my first choice behind a Bridgy. I looked one of them up, an 8520 is the basic type I would love to have. In fact, I am not so sure I would not prefer it to a Bridgport due to its smaller size, the ability to easily break it down for transport etc. Anyway, it would be near my top choice to be sure.
Another reason this machine would be high on my list of choices is the fact that it uses 2MT collets which the little Atlas I have already uses (less tooling to get started) plus, given my space issues here I could far easier accomodate a machine of that size than a Bridgeport. Not to mention the fact that in reality, I am a hobby shop guy and I could not justify the cost of a Bridgeport plus tooling simply for me to play around. I just have too many little obligations (3 in grade school) to allow for that at all. However, I might be able to unload enough of the toys, other tools or machines etc. to cover the expense of one of these machines.