Help with earphone impendence?

I just bought a brand new pair of Panasonic RP-HJE900 Zirconia In-Ear Headphones. Im about to buy an mp3 player. But im a little noobish at this. I've read how great cowon's are at sound quality. But i dont really understand impedance. The HJE900's have an impendence of 26ohm's and the cowon i9 i was looking at said it has a maximum output of 16ohm. Im not really sure what this means to me. What effect will this have?