It's not the price or suggested power of the psu, it's the quality. Poor quality supplies very rarely are actually capable of their "rated" power output. Less powerful quality units will go to the max and sometimes beyond.
I cannot say that I have heard of Ace as a manufacturer of PSUs, or anything else for that matter.
The big quality names include XFX, Cooler Master, Corsair, Antec, Silverstone and Seasonic but to name a few.
As a good guide, look for 80+ efficiency PSU's. And a 550W supply should be well capable of supplying that little rig.