While we, unfortunately, do not have more thorough testing to back this up, based on what we have seen, we would thoroughly recommend the be quiet! SFX L Power as a solid, well-made power supply.
eTeknix has published a review of the be quiet! SFX L Power 500W. The editor loves the power supply, giving it a raving review with nothing but pros (like the excellent design, modularity, efficiency, and low noise). They couldn't get it to work on their specialised benchmarking setup, but the PSU ran flawlessly in regular builds. This proved enough for the editor to give this PSU the Editor's Choice award.