I'm looking at the new Seasonic X-series and Platinum series power supplies but am very confused about the part numbers.

For example, with regards to the new Platinum 660W part, I see the part on the Seasonic USA site (http://www.seasonicusa.com/Platinum_Series_XP2.htm) referenced as SS-660XP2 (sometimes the "2" is superscripted, other times it is not). But on Newegg, it looks like the same part is listed as SS-660XP without the "2". Are these the same or different parts?

Or with the Platinum fanless 520W part, I see it at some web stores with the "2" ("SS-520FL2") and some without ("SS-520FL"). Are these the same or different parts?

These parts are all so new that I doubt they came out with an original version and then quickly replaced them with a "2" version.

In the review of the 520W Platinum Fanless PSU there's an addendum on the last page, in it MikeC wrote:


Perhaps Seasonic thought this little correction was enough to give a different part number to the newly produced PSUs?

I just spoke with the Sales Manager for Seasonic USA. He says the "2" denotes the newer parts that are 80 Plus Platinum while the ones that don't have it are the older 80 Plus Gold models, which are now discontinued.

The funny thing is that I've seen the old and new in the 400W and 460W sizes but don't recall seeing an older (80 Plus Gold) 520W model...I thought they just started offering the 520W model when they moved to Platinum. However, the Sales Manager says they did have an 520W 80 Plus Gold.

However, its clear to me that retailers are confused by the numbers as some do seem to be using the "2" and non "2" part number interchangeably, sometimes in the same listing!

Agree that retailers aren't usually very good with part numbers.
The original SS-***XP platinum units are all listed here:
http://www.seasonicusa.com/Platinum_Series.htm
So there were no units below 860W in the Platinum XP series. Therefore when retailers leave off the '2', when refering the Platinum-560 Fanless or Platinum-660 etc it is just a typographical (or some other kind of) error, but they are still talking about the new XP2 units.

The XP2 units have various improvements over the XP units, most noticeably smaller case size (190mm deep vs 160mm), but probably some other things under the hood. There are sometimes differences between the modular interfaces of difference generations of Seasonic units (eg KM and KM2 use different modular interfaces) - don't know if this is the case between XP and XP2.

I think the sales manager you spoke to was probably thinking of the X-560 when you were talking about a 520W 80 PLUS Gold model; they definitely don't/didn't have one.

Seasonic's 80 PLUS Gold units have different part numbers.
The original X Series (X-650, X-750): SS-***KM
Second generation (X-560, X-660, X-760, X-850): SS-***KM2
Third generation (X-650, X-750, X-850): SS-***KM3
X series (X-1050, X-1250): SS-****XM
IIRC the SS-***FL (eg SS-400FL, SS-460FL) were KM2 units also.

So the Seasonic sales manager you spoke to was incorrect about the '2' denoting efficiency.