The 780's don't really need an amp but will benefit from one like most cans. The ones I tried sounded great out of my netbook and the guy I borrowed them from used them primarily from his ipod. I've tried both the Beats and 780's and much preferred the latter. The Beats were a little too boomy for me and didn't really impress me. With the 780's you can feel the bass which is a great feeling. Of course it all boils down to personal preference in the end. Where are you located? I know of a place to get some sones pretty cheap depending on where you are.
Personally I'd order the sones and then go and try the Beats side by side. If you end up liking the Beats more just send the sones back.