The collected works of sevenspirals

The Pioneer 305S is the way to go. I've personally used them to load Irix 6.2 and 6.5 on an Indy, Indigo2, O2 (externally with a 68 -> 50 pin adapter), and on an octane 2. They are fast, quiet, and smooth operating. They support audio over the bus (verified) and they are usually plentiful on Ebay and elsewhere. You might get "lucky" and end up with a really weird one like this one I bought recently after this thread reminded me I loaned out my 305S and never got it back:

Long-arse link to ebay:
http://tinyurl.com/q7m6dag

I have no idea why it's light blue like that. I have some fantasy that it came from a a cool Unix machine from a secret back room at Bell Labs, but it was probably pulled from the belly of a light blue Pop Star! Karaoke machine which fritzed out after the clown fell on it during the birthday party.