doesnt the r-9 have an opti-in
if so, id stick w/ the AD-20, but if it only had analog-in, id go w/ an mp2 as well, maybe even an aerco mp-2 if you could find one used
if the r-9 has digi-in, what about a ua-5
but like i said, if it only has analog in, an mp-2(SD) would be great, or what about the beyerdynamic mv-100? anyone heard peluso>mv-100
or what about something diff and trying an RNP(really nice preamp) i recall bush running one awhile back and liking it, just another 400-ish option