If you want the best bang for the buck, look for a vertical, or universal (horizontal with a vertical head that swings out of the way) K&T (Kearney & Trecker/Milwaukee) or Cincinatti mills in the number 2 size. Depending on model, they'll weigh 3-5k give or take, but they're beasts.
You'll need 3ph or a 7.5 or 10hp Rotary Phase Converter (a great investment, you can get an American Rotary 10hp for around $1k, that's digitally controlled and CNC ready, and you will find the world of great machine deals open up once you can power 3ph equipment) to run it, but they typically have mechanical (real) power feeds in each axis, rapid traverse in each axis, and even a clapped out one will machine circles around any bridgeport, and hold tighter tolerances. You can often find incredibly nice ones for anywhere from $1000-3000, I've seen them frequently in excellent condition with accessories for $2500.
I'd probably stick to looking for a vert, unless you know you'll take advantage of the horizontal's capabilities, of which they excel at many things, but mostly not things knifemakers need, and the vertical models, usually have a sliding head, which is useful. The only feature you're likely to miss is a quill, which bridgeports have, but are honestly, a weakness of the machine. It's nice because it does double duty as a drill press when you have a chuck, but you should typically never use the quill for anything else, and it adds another point of failure and slop.
These machines don't take anymore space than a bridgeport, except work envelope if it's got a bigger table than a bridgeport, which many do.
Also, there are some smaller machines, like the rotary head models, which are really cool, but probably not necessary for you, and of course, much bigger models, that are likely too much for you to move.
These machines are true industrial beasts though, and only sell cheaper than bridgeports because most people are afraid of trying to move them. They're shorter, and less top heavy than a bridgeport though, and honestly, easier to move if you understand how. I've moved mine between 3 shops, and all around each shop, with pinch bars and pipes or round bar every time.
I've got a K&T No 2H vertical, that weighs about 4400lbs as I recall. Love it, hate my bridgeport (clone), and consider them overrated, even when they're nice and newer. If you're determined to have a Bridgeport style mill, the Wells/Index knee mills of that style, are far superior, but still have many of the same limitations.
Power feed on a bridgeport table is pretty much useless for anything other than light facing. I can engage the power feed with a 6" face mill on my K&T and hog an inch of material off per pass if I wanted to. I've literally ripped an 8" Kurt Vise off my table and turned the cutter to lava when I made the mistake of only having 2 3/4" bolts holding it down.