550W is enough but if you can put a bit more money into the PSU, get the EVGA G2 550W as it has slightly has better components than the GS. The GS is a good unit, don't get me wrong.
It's a Seasonic. Despite the FDB fan, it's still pretty loud under load.
Yes, 550 should be plenty. The 311 watts PCPP gives on your parts list is worst case of everything running full throttle, which very rarely happens. I'd estimate you'd pull around 50 watts at idle and maybe 200 to 250 while gaming. This leave you a decent amount of room for a CPU upgrade and/or single GPU upgrade in the future, but won't be enough if you plan to eventually use multiple GPUs.