Mach3bass and BBE on the X5 will only hurt sound quality even more when you use them with a good IEM like the UM2. These features are designed to enhance the quality of stock earbuds and cheap consumer phones, not professional-quality stage monitors like the UM2.
Out of all DAPs that I've had or heard, I think iRiver tends to boost the midbass and lower treble on their players slightly in order to give them a punchier sound. However, the H120 hisses far too much to make a good pairing with the UM2 unamped. I think the H10 actually sounds pretty good from what I remember, but I haven't tried it in a long time, much less with high-quality files.
The Kenwood HD20GA7 has terrific bass, deep, texured, controlled, and very strong, but the hiss levels with the UM2 are completely unacceptable. Too bad really, since it would be perfect otherwise.
I think you're SOL. If you want more bass, get a bassier phone. Try using Comply tips on the UM2, or get the Super.fi 5 EB.
Originally Posted by Veggie_Musician Well I have a pair of UM2's!
Well. You also can't expect much bass from IEMs. Have you tried with an actual set of cans? The bass is much more pronounced. There isn't too much you can do unless you can find a player with decent EQ/SQ. I'd recommend iRiver 120/140. I've read they have the best equalizers of all DAPs. Iaudio is good too.
The Zen Micro also has a bass roll-off, marginally less than the iPods. They do not sound any bassier than iPods in my experience, and the EQ is quite limited (though obviously less so than on the iPod).
As you had the Vision, you more or less know this, just wanted to clarify.