http://www.amazon.com/Thermaltake-Automated-Supply-Oversized-Supplies/dp/B005F778JO/
That's what I use, personally. It makes it fairly easy to test a supply since it will turn red and start beeping furiously if you are not getting enough juice. I don't test a ton of power supplies, so I can't speak to bulk usage/lifespan, but it has been great for my needs.