best AD convertor under 100 $ ?

[asap audio]

Get an ART Project Series USB tube preamp. $100. It sounds good and gives you some adjustability. High Pass filter and input and output.
It will sound better than your Audigy. You don't have to load any software. Just plug and record.

It's competitive with some other much more expensive gear I have. I use it to record on the road with a shotgun mic into my laptop. For voice it works better than it should for $100.

[TurboJets]

Back around 2001 I upgraded from an audigy to an echo mia and found the different in quality of capture and headroom to be heads above the audigy.

the m-audio stuff is a step up though too, although there seems to be a little more headroom with the echo stuff in the $100-$150 price range but you wouldn't be unhappy with an audiophile 192. IME/O it's a big step up.