SZ680/660: Circuit city or online shop?

I'm most likely to get a sz680/660. Does anyone know the difference between the two? (the 660 isn't even on sony's site, but is the retailer model).

Second, I'm not sure where I should buy it. The problem I constantly run into with electronics is is the first model I buy is usually defective (dead pixel, whine, loud, etc), as it seems no-one does quality control anymore (except for perhaps apple), and minor defects with electronics I spend 2k on drives me crazy. I can get the 660 for $1,939.79 online (pricegrabber, including tax+ship) where circuit city will run me ~$2300 after taxes. So circuit city is $300 more, but if anything is wrong I can swap it the same day. With an online shop I will have to gamble that they will return it with a single dead pixel, and if they will I will have to ship it back, wait for a replacement, and hope the next model they send isn't defective. I'm not sure if $300 is worth knowing that if something is wrong I can get a quick replacement.

 

I looked at Bizrate.com to even find vendors for the 660 and it looks to be a 650 with the Sprint WWAN installed.

The 680 you are only going to find in more build-to-order instances from vendors that either build different configurations from Sony or from Sony itself.