I have a pair of Ultimate Ears 600 (UE 600 if you will) and while the headphones sounds truly phenomenal, they do lack a bit of punchy bass. The bass and low frequencies are still clearly there, but the bass is just not punchy. So, for overall sound quality and performance, which amp would be better? I've been told the e5 has a nice bass boost but the e6 sounds better overall. Let me know, thanks!