We use a good number of those DPS-2000bb models, which is basically the same model just rated for more power, and they are really great. They can put out HUGE 12V numbers, and they are rated for 92% efficiency all the way up to 125% of spec! They can be had on ebay for cheap, but keep in mind that setting them up is not exactly easy, and is beyond the scope of what most people are capable of doing, even among a typically tech-savy crowd like bitcoin miners. Setting them up with ATX PCIe plugs and making a nice, neat, plug-n-play package is worth something to someone who can't or doesn't want to take the hours it takes to build one, but I don't think it's worth $300.
We had 3x 80mm fans taped up on the side, and it was not enough to keep it cool. We could only run the PSUs ~40-50% (800-1000W) before they'd overheat and cause issues. We've upgraded to 3x 60mm delta fans, and they're loud, but absolutely amazing, and the PSU has no issues going to 2000W and beyond. So yeah, I'll agree that a single 120mm fan probably isn't enough to keep the PSU cool.
One of our PSUs in action.
How about a back view to show off our new PSUs! We've had them for a while, but just got upgraded fans so we could run them @100%.
Those are 3x 60mm delta fans strapped to the side of the PSU.
