for actors / models photos

If you're looking for high-quality professional portraits, then depth-of-focus is an important characteristic to a camera system you get, as is precise focus. For most of that you're looking at a camera with a larger sensor, preferably a FF camera since larger sensors allow you shallower DOF, thus giving you more control over it. You can get similar effects on a smaller sensor camera like the m4/3 format ones, but for that you'll need to go with fast lenses, which tend to be less sharp at the fast end (which may not be a horrible thing for portraits if you're looking for some softness). The only fast lenses you can get on the m4/3 format are adapted/legacy lenses, which are MF only.

If you're just looking at taking portraits that don't need to be stunning, you can do it with just about any camera as long as you have decent lighting. Lens-wise you're looking for something in the 80-120mm (35mm equivalent) range for portraits since that seems to produce the most flattering perspective for portraits.

I can't make any specific camera recommendations. I've taken some decent portraits with my GH1 using my Canon FL 55/1.2 lens, so I know that combination works well, but I have nothing to compare it to.

Just my $0.02