Hmmm...I can't give you any good pairing with the C5 given that i have never used that amp before, but I do have some IEMs in mind that perform rather well in terms of bass.
I'm assuming that you're a basshead, since you are looking for an amp with bass implementation and an IEM with bass?
If that is the case, do check out this group.
They have complied a list of all the bass heavy IEM that would suit your taste. From the list, I would recomment Velodyne vPulse (~$90), and Shure SE215.