best bargain site for IMAC memories and SSD?

[ws00297440]

Hi, Im thinking to buy the new Thunderbolt 27'' imac

BUT that 16GB memory ($567) is such a rip off.

I ebayed the memory and it only costs $169 http://cgi.ebay.com/16GB-4X-4GB-RAM-MEMORY-APPLE-IMAC-DDR3-1333MHZ-NEW-/260745871176?pt=LH_DefaultDomain_0&hash=item3cb5aa3f48

But I dont know the credibility of this product

so I need you guys help.