I would recommend asking Tim for a Grandstream. Although I don't have one myself (connecting via Asterisk), there have been some flukey issues with at least a few accounts connected via PAP2, and the Grandstream will be the officially-supported device after launch.

If you want to keep your PAP to tinker and/or play with pay-as-you-go providers separately, $50 is not a bad price (you have to decide if it's worth $50... ), but for the purpose of getting in on this Beta, I'd request a Grandstream.