Get the Alpha or the Swiftech.
The alpha using a much quieter fan with less CFM's but is almost as good as the Swiftech with a 80CFM Delta. Also, The Swiftech with the same 80CFM Delta out performs the Alpha by .5C and .01C/W. With the 50CFM Suron the Alpha out performs the Swiftech with the same 50CFM Suron. And remember the 80CFM is LOUD, very loud.
Check out this post it might help.... http://forum.oc-forums.com/vb/showthread.php?s=&threadid=79590
but the Alpha or the Swifty is the way to go, anything else is just wasting your money. Best Bang for you buck would defenitly be the Alpha with the 50CFM suron. And it is more than ample for your 1.6 to be running at 2.0-2.6.
BTW, 2.0 is not to high to use a air cooler, you could get into the 2.4 range before I worried about water. The Northwood is a very cool running processor.