Seller has a bunch of options, including the stock power supplies for $100 less and rails for $40 more. They're quite reputable and I've personally visited their warehouse back when I lived in Texas.
Seeing as the SQ PSUs run $100+ each and the backplane is another $250, I'd say this is a pretty good deal. They don't take offers, but seem to have lots of inventory.
SuperMicro 4U Barebone CTO Server SAS846A 2X PWS-920P-SQ | eBayhttp://m.ebay.com/itm/382176300456
Seeing as the SQ PSUs run $100+ each and the backplane is another $250, I'd say this is a pretty good deal. They don't take offers, but seem to have lots of inventory.
SuperMicro 4U Barebone CTO Server SAS846A 2X PWS-920P-SQ | eBayhttp://m.ebay.com/itm/382176300456