I hate to say this, but while more overhead capability would be desireable, the original question regarding the XFX 650W's suitability is still "YES".
Regardless, take a look at the ratings for each of the recommended PSUs before you buy. Both the Silverstone and the Corsair (by a huge margin) have much better ratings than the OCZ.
What is your budget? That will drive your decision greatly. If money were no object (can anyone ever really say that?), I would recommend a Seasonic (as JohnnyLucky indicated), they are truly excellent PSUs.http://www.newegg.com/Product/Product.aspx?Item=N82E16817151087