Welcome!
I've only had my R-09 for three months or so. I recorded several sets with the internal mics (I had nothing else at the time) and they will work in a pinch (better in certain situations than others), but external mics are the way to go.
I also would recommend Chris Church's equipment which seems to work very well with the R-09. He has a good special running, I think. If not the prices are still very reasonable.
The R-09 FAQ here is a great resource and I'm sure the experienced tapers will give their opinions at some time. Everyone here is more than helpful.
But ... since you asked, I've always read to not use the AGC so I never had. I've always set my mic gain on low when using external mics.
I've done primarily open recording so I can't discuss stealth intelligently.
If you have the R-09, but no mics, I'd go out and record some bands in clubs if you can, just to become familar with the unit, setting levels, getting used to it, etc. I've made listenable recordings that were OK for me.
Have fun! rWc3523