For your money I would be considering the Clip+, put rockbox on it then amping with C&C BH portable amp. You will be double amping which means you will be feeding the amp from your Clip+ headphone out which is highly frowned upon here, but will give you IMO the best sound quality for your money IF you want bass and clarity.
You can read about the amp here.
And because I'm in a good mood you can even have a photo of what it would look like.
Other options you could consider is Cowon C2 which supports EQ like Mach3Bass offering improvements along with other enhancements, it's small and has good battery life but seriously if you want loud volume levels and clarity you should be considering the rig I mentioned, because the C&C BH has an LF switch which boosts bass and clarity, that is the switches purpose, along with other features such as dual headphone out and soundstage expansion.
That's simply what I would do after messing with several sources and never being happy, others might say differently and I suggest you listen to any other options given to you, because we all think differently.Edited by H20Fidelity - 5/2/13 at 5:44am