I keep my computer in a cabinet, and I'm thinking of venting the cabinet with a 92mm or 120mm fan. I've got a few lying around, but I'd need to plug it in to a wall outlet. Should I just use an AC->DC ...

The CPU OPT header is an additional connection for special processor cooling accessories, such as specialized coolers with multiple fans or water-cooling components. Functionally, CPU OPT is identical ...