But why? The average 80mm fan draws very little current, it would take about 6 or 8 of them to equal the load of a single hard disk.
Get the kind that run off molex drive connectors, some Y adaptores and hook them up all nice and neat...or better still, splice the wires putting them in parallel and routing the wires in unseen parts of your case and bring it all out to a single molex connector...
Unless you are going to get really ridiculous --like with 30 or 40 fans-- you won't hurt your power supply.
Plus... keep in mind, more fans are not always the answer. You can almost always get by with one or two fans in a well ventilated case.
Im really wondering WHY?
The worst most powerful casefans only draw 12-15W tops... and if you are that close to your powersupplies load limit then you really need a better PSU as it would probaby burn out soon anyway!