Enermax Platimax issue : serious ?

Hello everyone,

I registered on Jonnyguru 'cause it seems like it's the go-to place for everything power supply and I'm in dire need of help / information / advice from all the pundits out there :)

So, long story short, I bought a brand new Enermax platimax 1350w in late Januray, installation went well. At the time, I hadn't really pushed it, only used the PC to work and some very light gaming, so the load on the monster was fairly limited.
Three days ago, I received my final graphics cards (2 GTX980) and my Philips BDM4065UC, 4k 40" screen. When I started playing demanding titles on the PC in SLI with all the details crancked up, the PC started to make a rattling and hissing sound that really got me worried. I inspected the tower to try and see where it came from, it comes from the power supply. The noise is really distracting and frackly, to me at least, it feels like something is really wrong down there. I tried to determine whether it was the fan, but I don't think it is, sounds more like an electrical thing.
Here's a sound recording so you guys can have a better idea (two different recordings mashed actually) : http://ift.tt/1PIvYtt
It doesn't do any of this under low load, only when the load ramps up, so does the noise.

Bottom line, here are a few questions : is this normal? am I taking a risk letting it run for now? Should I RMA the PSU? What could be wrong?

Thanks a lot in advance for your guidance :)

Enermax Platimax issue : serious ?