I'm similar on this. I run a 980ti/i7 4790k on a Silverstone SFX-L 500W in SST-FTZ01B case. That happily runs inside a 500w PSU and it doesn't have any issues. I guess as others have pointed out, it's the ability for the said rails to deliver a stable supply.
I'd also hazard a guess that the 600w minimum is aimed at hobby builders rather than OEMs who have some level of design and build expertise. In my rig, as it literally has the motherboard/cpu/ram/gpu/ssd, there isn't a whole lot of other stuff to power. I'd guess the 600w minimum is aimed as a safe bet with some headroom for a few extra cards/accessories etc.
As others have said though, I'd take a quality PSU over the cheap "750w honest guv" PSUs anyday.
I also don't fully despise PC World. They have a time and a place, that place might be minimal for us who are professionals, but it's still occasionally got us out of a pickle when we've needed something immediately.
Biting the hand that feeds IT
