Check your emails if you have a PG account or have bought something from them recently (UPDATE: See below for more details).
I received an email from them this morning entitled "Take a survey, get a $20 gift".
It didn't take long to complete and I then received an email with a voucher for 20 USD.
I currently have FX 2 Pro and Amp 2 Pro and I can upgrade either one for 50 USD each.
So I will probably use the voucher to get FX 2 Elite for 30 USD.