Austin, I'm not sure I follow you with regards to ROM rankings? One seems the best, one is a bit better, and yet another seems the best? Please clarify...
Sent from my Nexus 7 using Tapatalk
Sorry about that. Please keep in mind that this was not scientific in any way and purely my subjective opinion based on leaving myself voice-mails and calling friends/family for their feedback.
I basically grouped the ROMs into 3 categories, Sense-based, AOSP/AOKP based, and CyanogenMod based. Of the Sense based, CleanROM was the best sounding for me. Of the AOSP, none really stood out but all were better than the sense based ROMs. And then finally, I only tried the CM nightlies but the few I tried were the best quality of them all. I have no idea why this would be but I did read somewhere that CM upped there "bluetooth spool" above what was in the base google code which supposedly increased the audio quality of bluetooth streamed music. No idea if that has anything to do with bluetooth headsets and outgoing voice quality.
Again, this was all subjective by my ears and those of my friends/family. You may find the opposite is true. I would say, if you're comfortable with ADB/Fasboot/RUU's, it's worth trying out a few ROMs to see if any improve your headset voice quality.