Back at Macworld, we laid our peepers on Western Digital's MyBook Thunderbolt Duo and were able to take a demo setup for a quick spin. Now, the dual-wielding external HDDs are officially on the market. You can snag 4TB (2x 2TB) and 6TB (2x 3TB) versions of this "über-fast" MyBook for $599 and $699, respectively. Don't forget: you can daisy chain up to six of these bad boys via the dual Thunderbolt ports on the kit's backside (if you have quite the piggy bank, of course) -- just like the four-unit set we
