I think I was a person responsible for initially promoting the JM6 Pro as a good match for the PR2; I run my mouth quite a bit on audio related social media channels.
Yes, I did notice an improvement with it over the 1Vrms Apple dongle. The sound is more open, dynamic and impactful with the JM6 Pro.
However, a trusted source informed me of the following last night:
Whizzer DA1: Review and measurements
While it's nearly double the cost of JM6 Pro, it's more powerful at 2Vrms and 70mW into 32ohms, with less distortion. It's based upon the ESS Sabre ES9270 chip.
It supports an inline microphone, like the JM6 Pro, which is important to me because I will be making and taking calls with the PR2 attached to my phone.
I thought I'd check it out for myself and ordered one.
If it pans out the way the measurements indicate that it will, I think we'll have found the cleanest, most powerful, least expensive DAC-AMP dongle available with microphone support. I'll know for sure in ~2 weeks.