Hi krone9,
That PSU works well in our experience.
Are you still having poor efficiency with the cube? If so, we offer a 30 day warranty replacements on all of our products and are happy to offer one on one troubleshooting as well. If you are interested in either, just send us a note (support@jonesgear.com). Please include your order number in the email. A screenshot of your Cube's config page (while hashing) would help as well.
Regards,
Kevin
Jones Gear