Heatsink Fan Adapters

Thinking about trying to make my two computers quieter, but don't want to lose the cooling ability...especially now that I just bought an AMD XP 1800+. Has anyone read anything lately about heatsink fan adapters? Would love to have an 80mm fan on my copper Vantec HS. Some of the new adapters have slots in the side which pours air, not only over the center of the heatsink, but also out the sides. Is this a good design or are there better ones? Also, where is a good place to buy a couple of these adapters? Thanks for any help you can give me.