Check the NGK website, it has information on which can be used. I agree with Pro5Monkey, best keep with the OEM ones. NGK has copper or platinum, I replaced mine with the NGK platinum and it ran a little smoother - could be just because they were new plugs.
As an interesting side note, the Bosch USA website does not recommend any Bosch plugs for the Mazda Protege - which probably explains why some forum members had issues with Bosch plugs. (If you do a search)