the AD-20 is an analogue to digital converter. It will not work with the R-09 because the R-09 does not have a digital input.
I recommend getting the line transformers. This is almost my exact first rig. I ran SP C4's>PS-2>line transformers>Edirol R-1.
Depending on your taping environment, you may not have enough gain to have a solid signal. The line transformers will at anywhere from 10 to 20 db of gain (depending on what you get). With the line transformers, I never had a problem of not having enough gain.
Good luck and you will make some good recordings with this rig.