I have a PR-20 at home, working with a 710 Leslie. I LOVE the sound of the tone cabinets along with a leslie!! The tone cabinets have a very rich tone and give an harmonic blend that you just can't get from the leslie alone.
The PR-20 is actually a home unit and only has a 20-watt amplifier. If the church is small this unit will yield good sound. If your friend has a large church however, he may want to look at one of the large tone cabinets that have a 40-watt amp. (Same wattage as the 122 & 147 leslies.)