Thanks for mentioning the WAMI Recorder - I hadn't come across that before, so I've added it to my list of projects and websites related to recording audio online. I'll look into it in more depth when I have time.
I seem to recall hearing that peer review was a planned future feature of the "new" assignment module - and I think that's the best place to focus any development effort on peer review, as it'd allow for peer review on any assignment with any combination of submission types (including Online Audio).
In the mean time, I'm not sure what the peer review assignment type you refer to is - a quick search only turned up an old-looking 1.9-era plugin, but the Workshop module seems to be intended for peer (and self) review. It's not the most elegant solution, but you could potentially use the Record Audio repository plugin in conjunction with the Workshop module - you'd just need to provide some brief instructions to let students know that they can/should record by clicking on the "Add..." button in the file manager and then choosing the Record Audio option on the left. Unfortunately, it doesn't seem to run the list of submission files through filters, so you don't get an embedded player - just a download link - which also adds to the complexity.