I would look at the Corsair 550VX, Antec TP-550 or the Seasonic S12II 520W, either of those three would have no problem powering you system and can handle a more powerful video card in the future. If you are on a slightly tighter budget an Antec EA 500D will power it fine too, its not quite as nice as the first three but its still very good.
The wattage rating on video cards is done using a very high end system so its exaggerated quite a bit, but HEC PSUs are pretty crappy and those are the type of unit they exaggerate the rating for, because even a POS 550W HEC unit can handle a 5770, but a 300W HEC unit doesnt stand much of a chance for long.
The Seasonic is a bit newer than the Corsair 550VX, and TP-550 and performed extremely well in a review at jonnyguru so i would take it over the 550VX especially if its a bit cheaper too, the TP-550 has the advantage of being modular but if the shop doesnt carry antec any more it doesnt matter.
I would take modular over the extra wattage, more wattage wouldnt hurt anything but you arent going to use it with your setup unless you add in a second 5770 in CF, modular makes it easier to deal with the cables since you have fewer.