I would probably get it from a place you can return it easily, like amazon, their policies are really good, they even ship you a replacement before your return the other, and if the replacement has the same they probably will give you back your money.
Yeah, I prefer Amazon to Newegg, but it's hard to tell which model they have on Amazon. This page shows the SS-760XP model number, not SS-760XP2, and the picture is blurry but seems to be a different model: http://www.amazon.com/Seasonic-ATX12V-E ... PDKIKX0DER
Then again, this thread would seem to indicate that there weren't any 760W PSUs in the original XP series, so it should by definition be an XP2: viewtopic.php?f=6&t=65857
So it could just be a slightly wrong model number on Amazon. Wouldn't be the first time.
Amazon is really bad into updating models, this has happen in a lot of items i have bought in the past, and by the following im not garanteing you that it is the XP2, but if you read the review on the Seasonic PLATINUM-860 ATX 860 Power Supply, Be careful -- model changed but not model number
This looks like a good power converter. It has solid output current at the main rails, good current on the secondary rails, and tight voltage regulation across wide loads for all rails. It includes a number of connectors, all of which look reasonably well constructed, and things fit together nicely.
Unhappily, the Platinum-860 ATX that I received is not the model advertised here. Yes, it is still a Seasonic Platinum-860 ATX, but there is a tiny (might look like a printing error if you need glasses) additional character in the model number. Instead of an SS-860XP, it is an SS-860XP(2) -- the (2) is actually superscript, and about a third the size of the other characters.
Im not sure if the previous model is still in production or sold (maybe there is inventory still), my guess (again cant guarantee you anything, so if you buy it its at your own risk), is that its the XP2 even if its displayed as the XP.
If getting the XP2 is important to you, and you want to be more i would try the following,
1) Try to post comments on the last reviews on the 760 to see if a someone that just bought it can confirm if its the XP2 model.
2) Write to amazon, see if they can get the SKU or the model number.
3) Write to seasonic to check if the XP is till in production, my guess is XP2 replace it but you never know.
Personally im also looking for PSU to move into SLI for 4k, but probably wont be until next year, i dont think a SLI of gtx780 can move well 4k, but hopping the GTX880 can, but will see. Maybe by then Seasonic has a new iteration of their platinum series with the coil fixed for good now, its a minor thing but they are getting bad rep on it.
As an alternative, Corsair RM seems like a cheaper option, even if its not getting the same scores as the seasonic platinum, its more a value oriented series targeted to replace the TX series and gain very quiet operation and fully modular. You could buy shorterm for just the GTX780, and upgrade to a better PSU when you upgrade to sli, for this i would invest the least, Corsair RM Series 550 Watt ATX/EPS 80PLUS Gold-Certified Power Supply - CP-9020053-NA RM550
or you could invest $20 more and go for the 750 and stay like that, Corsair RM Series 750 Watt ATX/EPS 80PLUS Gold-Certified Power Supply - CP-9020055-NA RM750
Amazon has a lot of Kingwin Platinum LZP Series, just most of the them are from 3rd parties, so returning might be a mess. But thinking on a single GTX780, amazon do carry the KingWin Lazer Platinum Series 550 Watt Power Supply with Universal Modular Cables LZP-550
, same that got the SPCR editors choice, Kingwin Lazer Platinum 550W Power Supply
Good luck with your choice,