Being able to plug in an external microphone is a BIG plus when trying to do field video with any kind of quality sound, even if it's only through a 1/8" miniplug. It's not that onboard microphones are bad these days, it's just that they capture sound TOO well from all directions, so you can't isolate what you really want to hear like you can with some kind of unidirectional mic. (Edit to add: Being able to use an external mic also is a good way of avoiding the original issue of zoom/focus-motor sound, or even handling noise -- moving a finger even a fraction on some cameras make it sound like you're in a thunderstorm! After first sending my post, I remembered that this was a fairly common issue mentioned in several camera reviews.)
When I was looking for a camera to replace my Sony with a failing mini-DV tape recorder, it seemed the that only reasonably prices camcorders with mic jacks were Canons. I went with a Sony again, but the cheapest they had with mic input was $1200 (in some ways I regret spending that much, but for one thing -- the onboard image stabilization is AMAZING on it), while from what I remember, the Canons were more in the $300+/- range. A surprisingly good inexpensive mini-plug microphone is the Audio Technica ATR6550 mini shotgun mic, at about $50-60. I cant recall whether any of the other brands even offered a mic jack option, but for me with all the live music I film, not having one was a deal-breaker for me.
For picture, for the most part, the HD capture in bright light of most new cameras is going to be fine, but you may want to check reviews for low-light capability, as this can really affect final quality in dark settings, with some cameras really adding a lot of grainy noise when they try to artificially boost the signal. There is a limit here just because for any camcorder, the lens is too small to really excel in low-light conditions, but to get a camera where this isn't an issue means thousands of dollars, not hundreds.
Sorry I don't have specific recommendations, but after looking around myself, I find that the 2 most important factors on where a camera sits on the overall scale of performance (and often price) is 1. Audio capabilities, and 2. low-light capture, so keep those in mind as you check out your options.