Good advice on Linux (debian) compatible microscope

[deloptes <deloptes@gmail.com>]

Hi,
I read some time ago a discussion here about microscope and I am thinking
for long time to buy one.
I have no idea what I have to look at, so I hope someone would help make the
right choice. Here are some of the requirements and questions I have

Req.
        400x zoom is OK, but I saw also one with 500
        price <=200,-
        stand alone and PC use (implies display and USB)
        not hand held
        linux (debian) support

Questions
        the few I had a look at say they support AV out. What does it mean? 
        is the quality good enough? does such one supports also video over USB?
        the few I saw say they use Li-Io battery - is it reliable/replaceable 
        (I know that some Li-Io batteries are very rear.)
        it says also optic zoom 200 and digital zoom 400

Thanks in advance