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Definitely go to Mac Gurus (http://www.macgurus.com/) for all your internal & external drive needs. I've been doing biz with them for 15 years, & wouldn't consider getting an ext. drive housing elsewhere. Finest kind.
 
seagate's have 5 year warranties, which is why i bought one. as far as place, i like amazon. they have free shipping with some pretty good prices.
 
OWC has been offering great Mac products for 20 years. I'm using their Hitachi 200GB 7200rpm external, which matches my MBP's internal drive. Screamin' fast on the Firewire 800 port. I wanted speed and portability more than capacity, but now there are higher capacity models with matching speed. Check 'em out!
 
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