And a +20 to your next attack roll? Can you say "Power Attack"?
Well, you only get to leverage that full +20 if your BAB is already 20; otherwise you're just adding double your BAB to damage, with a bonus to hit. And that cost you a standard action to do. Bascially, if you can gain more damage from a single Power Attack than you could have done in a full round, it's a positive trade-off, but if you can't manage 2xBAB damage in a
full round, you probably shouldn't be in melee in the first place.
Wriathstrike, however, is quite nice for this purpose, and it's only 2nd level.