EDIT-EDIT: I am no pro, just a regular consumer that spent some time researching. Most of the nuances between the following models are highly debatable, and much is beyond me. But I have a firm grasp of most of the basics at this point.
EDIT: IMHO, to pay 800 plus dollars on camcorders with that kind of small sensor is totally idiotic. 1/5inch is not at all worth it. I am not saying this to be mean, but its a ridiculous decision, which I want to make clear. Not anything personal against you, I started out in the same boat. I am something of a Pany fan now (hey 299 for 3mos, who wouldnt be?) but, this is a terrible decision to make, if you want quality video.
As you read the site, focus on sensor size/video performance/low light. That is the key difference between those camcorders and what you should be looking at with an 850 dollar budget.
However, dont even consider something with less than 1/2.3 inch sensor for that budget man. 120GB hard drive is NOT worth crappy video. Especially not when you can get the memory WITH much better video for the same basic prices. Some examples to look into will follow.
What kind of computer do you have? Have you ever worked with AVCHD before? 4 hours of straight AVCHD on a weaker (relative to idea. for these types of files) computer would be a real problem to deal with.
But, since you are starting off on the wrong foot, I will list some models you might want to consider looking at:
-The Sony 550 series, some have had for approx 700-800, though I have not seen such deals myself.
-Panasonic TM700/750 are excellent camcorders, the same camcorders also have an HS Series which has hard drives, and the new 2011 base models will be in your price range.
-Canon M40 series just released, out soon. The 2010 series have received good reviews but, IMHO, Given the M40 has such (apparently) significantly improved low light, your application, and your budget, you should focus on it over the 2010 series. Well worth the extra cost, imo.