I'm sure you are okay with overclocking yourself, but if you can find the Gigabyte GTX560 SOC @ 1000 mhz core clock, that was king of the hill for about three weeks when it was available. Besides being fast, it is also the quietest. The Sparkle GTX560 Calibre also comes at 1000 mhz and has a nice Arctic Cooling heatsink. 1000 mhz is more than most reviewers have been able to overclock the other 560's on stock voltage. Other than those, I would go for the MSI Twin Frozr II, which is putting up amazing temperature numbers.
The Sparkle Calibre is also clocked at 1000 mhz, but in addition, has the highest clocked memory as well. I know you can always overclock yourself, but the reason these cards are so hard to find is that they are only using the best of the best chips and so are very rare and hard to produce.