What silent computer would be best for voice-over work?

Episode 1103
Mitch fromMitch does voice-over work and still uses a 2004 Power Mac G5. But the fan is so loud. So he's looking to get a new Mac Pro. Leo says that although it has a big fan, it's extremely silent thanks to it's central core design. But if he doesn't really need a lot of horsepower, the Mac Mini is very quiet as well. An iMac would also work great. That's what Leo would be looking at. It would be about $1200-1500.