Upgrade 3 year old OCZ 700W PSU?

[FlyingPig]

Hi,

I've got the upgrade itch for a graphics card and I'm trying to make up my mind about whether I should upgrade the PSU too. My 3 year old system:

i5 2500K CPU
OCZ PSU 700W Stealth Xtreme
8GB RAM
MSI P67A-GD65 motherboard
GTX 570

I was tempted by the AMD R9 PCS+ 290 graphics card going for 200 quid, but then found out it would be prudent to replace my PSU first.

My question: if that is the case, what if I decide to keep this 3 year old PSU, save my money and instead spend some extra cash and get the more efficient GTX 970 instead? Surely the OCZ PSU should be able to handle the 970 and that way I could avoid the hassle of replacing the PSU? (never done this) Or with that kind of non-premium PSU is it really a case of when is it going to fail?

As a sidenote: despite the name of the current PSU, it is actually quite loud and I think it is also what is causing my rig to "whine" a bit sometimes (not coil whine, more like some buzzing, some kind of resonance sometimes that is hard to describe), so perhaps that is an argument in favour of biting the bullet and upgrading it.

Any input appreciated.

 

[FlyingPig]

Thanks. I might just keep it and buy a GTX 970 (Galax).
In terms of "how a PSU fails", is it a gradual thing you can foresee or is it sudden and can it take out your motherboard and graphics card?
Main priority is upgrading my graphics but I guess at some point you have to invest a bit in your rig to keep it healthy and happy, just don't want to waste money.