android phones are VERY weak when driving headphones. they only thing they drive well is IEM's. the bad news is that an E5 is going to be a disaster paired with a cell phone. it will increase the output, but be prepared for constant interference from the cell phone radio and from wifi as well. i have an Incredible and i have an E5 and it did not work very well simply because of the interference.
i have tried several full size headphones with my incredible and none got loud enough. i tried the following: HD205, HD280pro, XB500, UR-40, HD428, UR-55. even with IEM's i'm 2-3 notches from full volume on loudly recorded music and either at full or one notch from full on quietly recorded stuff.
bottom line, is that the Incredible and also the motorola droid are bad portable music players. the only way it may work may be with an amp that is in a solid metal case to sheild from the EMI or EMF, whatever you call it. the E5 is mostly metal, but the 2 end caps are plastic.