I've heard good things about the Oppo and the Panasonic S77 seems to be getting favorable reviews.
I am a strong proponent of common sense, and common sense to me says that spending more than a couple hundred bucks on a DVD player is silly unless you have gobs of cash. HD player will be out. For quality, that is the way to go, and if money is tight, then saving your cash to get a HD player makes a lot of sense. A couple hundred will get you a good upconverting unit that will last for years.
If you just are hooking it to a regular 4:3 television then even cheaper models will do you nicely. Region free is hard.
Want to buy my old Apex DVD player? It only outputs s-video, but it is region free.