Your GTX-580 draws likely 40-60W more (peak) than a good GTX-970 (the real difference is under FurMark/OCCT, as your card doesn't have current limiters, so that it would draw 100-120W more). You might look at a good GTX-970 review (like ths one
: those were gaming AC figures, inclusive of conversion losses, actual DC ones are 10-13% even lower) to get a better power consumption estimate than the flawed Outervision's one.
I've found a couple reviews for this specific model (Gigabyte GTX 580 SOC) with ingame tests (mostly Crysis 2). The GPU pumps up to 270-280 W, or even almost 300 W with extra OC.
The kit CPU + mobo has been reviewed alone between 250-280 W (not ingame though, mostly CPU-intensive programs, some of which I plan to use). That's where my calculation come from.
But, as any be quiet, the P11 is overpriced: to say, it sports one of the best fans seen in a PSU (the Silent Wings 3), but it offers a just 5 years warranty, as well as the RMx with its inferior, cheaper fan (despite of fan and caps are the most prone to failure components in a PSU). Another marginally better aspect is the P11 load efficiency, but the RMx is rather close to Platinum levels. All in all the only "rational" aspect I see to favour the P11 is whether you wanted right a full-on fan PSU for some reason.
OK, thanks for your explanations, I see your point.
The RMx have a 7 years warranty, by the way, even the 550 one.
The G2 550 is not on par with the P2 550 sibling: though not really loud, it's more noticeable due to a more conservative fan profile, so that you should opt for either the P2 550 or the G2 650.
I can't say anything about LDLC, though I doubt they may sell a P-660 clone at that price, maybe is it an X-650 one?
At any rate, personally I'd use a Seasonic PSU whether I were pretty sure about a conveniently low ambient temp (the P-660 fanless range is strongly ambient temperature dependant, at high temp that fanless operation is rather smaller/shorter than the best competition), and a customer support who don't put objections to replace the PSU just because I say it whines (like the Amazon EU's one usually does).
The P2 550 doesn't seem to exist. At least, it's not listed on eVGA website in EU, nor found in online vendors. The G2 650 sells at around 115 €, overshooting the other options.
As for LDLC, it has been confirmed to be P-series clone
, it even shares the same casing. It has a 5 years warranty, though, 2 years less than the P-660. They also have clones of the G-series, the S12II-series and the platinum fanless series.
LDLC is aware that those Seasonic-made units are prone to coil whining. Several forumers from forum.hardware.fr have reported an immediate exchange or refund on the first call to customer support.
However, from what you say, the ambient temperature in my actual room easily goes up to 27-28 °C in summer time, or even 30+ °C on short periods of heatwave.
Moreover, a Corsair representative is present on forum.hardware.fr and can help for RMA (while the Seasonic one is gone since a couple months), which is quite convenient.
Looks like the RM550x is definitely the better option.