maxalge :
Not for a gaming machine no.
3rd tier is ok for business machines, or surfing the web etc.
Lower than 3rd tier = replace. Never screw around with the heart of your pc.
I have a Corsair CX600, which is powering up Asus M5A99X EVO R2.0, AMD FX-8350 with Corsair Hydro H100i and MSI GTX 970...for 1 year now. I don't see what's so bad in them. Know a lot people who have had CX series for 2-4 years now and still working great.
If anything, people are over-reacting on few bad examples that have come along.
They're just as good in gaming machines as they are anywhere else. Of course, not all of them though. Some of the Tier 3 psus are truly something that should be avoided in gaming pc, but not all of them.