Welp, gonna email the FMod folks and see if they can score us a reasonable license. I've heard from other devs that they're merciful to indies, so maybe it won't be as painful as I originally thought it would be money-wise.
Let's all hold hands and hope together!

It just so happens that I contacted them two weeks ago. I got a friendly reply in 24 hours. They are good guys. My question was completely different from yours though

I wanted to know if it was possible to get FMOD sourcecode without buying a commercial license. And they thought about it, and they are keeping that a future option, but the problem right now is that there are some legal issues and it would need a license restructuring. Anyway, my point is that they are very friendly and openminded. I'm rooting for you.
Oh, one little note though. I wasn't able to get sound working in FMOD through alsa dmix when I tried it. (dmix is a software alsa mixer) If no other sounds were playing, then FMOD sounds played fine, but otherwise no sound coming from FMOD. (the opposite was also true: FMOD blocked the sounddevice so other applications couldn't output sound if FMOD was being used..)
I think I'm going to look into that issue further if you decide to go for FMOD, because it's very weird.
Oh, and irrKlang was no good, I guess?
PS: I see that you read my blog message

I translated the most important bits to English in the comment following your comment.