There is another new to taping/this board thread active here with a lot of good discussion. Look at that since that is essentially the same thing but already filled in.
http://taperssection.com/index.php?topic=169526The AT853's are fine if they have the mod done so they won't distort at loud shows. They seem to come up in the Yard Sale regularly (like now in fact).
Decent mics are typically going to give you much better results than built-ins on a recorder.
As to pre-amp and battery box (which may not be specifically covered in that other thread):
Mics need power (a few have batteries in them but most do not, especially tiny ones).
A battery box just provides "plug-in power" for tiny mics (the AT853, Church Audio, Sound Professionals, etc.). Most small recorders can provide plug in power themselves through the mic input (usually that function needs to be switched on to work that way). Using a battery box (or a pre-amp) will allow you to record considerably louder shows than a recorder's internally supplied plug in power before the mic may distort from the sound being too loud. If you record loud shows you generally need at least a battery box. A battery box only provides power and may or may not result in a loud enough signal coming through to use the line-in input on the recorder as opposed to mic-in (make sure you turn the plug in power from the recorder OFF if you use a battery box or pre-amp and the mic-in input).
A pre-amp actually amplifies the signal from the mics as well as providing power to the mics. Most pre-amps provide phantom power (P-48) which is at a much higher level needed to power large full sized mics and not useful for tiny
mics. Some pre-amps provide plug in level power for small mics or are switchable to provide either plug in or P-48 power. Pre-amps usually provide a little bit of their own flavor to the sound of the mics (since it isn't a direct pass-through there is often a bit of a sonic character imparted from the pre-amp). A pre-amp will allow you to go line-in on the recorder instead of mic-in (so you get less of the flavor of the amplifier that is built into the recorder and more of that of the pre-amp). Pre-amps are generally more expensive. You may or may not need one depending on what you record, your taste, and what mics you have.
If you record loud shows with external mics you will likely need either a battery box or a pre-amp. Even if you don't need one just to handle the volume either is likely to improve the performance of the mics relative to running them from recorder supplied plug-in power.