Which headset do I need for 2006 Cervelo Dual?

The Dual has a 1" steerer, and the current top cap says IS-2 on it. Do I need to know anything besides those two facts? I’m completely lost on what, exactly I need. A link to a decent, mid-priced option would be great.

http://cgi.ebay.com/Cane-Creek-Black-IS-2-Integrated-Headset-/390310089840?pt=Cycling_Parts_Accessories&hash=item5ae04b5470
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