Looking for a good 1U 500W+ psu.

Hello everyone,
I'm trying to build a custom low profile pc case which pcpartpicker says will have a total peak load of 438W (84W i5 + 275W R9 390).

I notice that Seasonic (SS500L1U) and EVGA (in the hadron) have 500W 1U psus and was wondering if one of these would be any good for my project. I'm just a little nervous about using a 500W psu with a peak load that close to the max.

I came across these 2 gold rated 600W units but I'm not really sure about them:

http://ift.tt/1JUzVsv

http://ift.tt/1JUzUon

Advice will be appreciated.
Regards

Looking for a good 1U 500W+ psu.