The three sp20 batch is the best deal, if you purchase your PSU's wisely.
The SP31 is loud, but really not that bad- three sp20's would be louder
The sp31 is nice and neat, no random cables from power supplies.
Thanks, that's what I was seeing also. I've got a nice little 220v 30a circuit just sitting downstairs, but I think I'll save it for the next batch of 'home' miners. I've already got 6 of the sp20 and 2 s5 units running at the office because of the noise.