One of your 'HDDs' is an SSD which use very small amounts of power, easily less than 5W.
Modern HDDs themselves actually aren't that power hungry either, 10W on load probably being an overestimation. So adding a relatively small number of HDDs to a system won't make that much of a difference.http://www.guru3d.com/article/geforce-gtx-560-ti-sli-review/14
This shows a system using an overclocked i7-965, which is much more power hungry than an i7-2600K, drawing 449W at the wall under an unspecified load.
They probably recommend a 700W+ PSU because they personally feel that stressing a PSU beyond 50% is a not something they are comfortable doing.
However with a high quality unit the only possible reason not to is if the PSU has a noisy fan/too aggressive of a fan controller, which I don't think is the case with the Antec Earthwatts EA-650 Green.