If the goal is just to get more volume out, I am pretty sure a CmoyBB can do a better job. However, amping is not about getting loud volume (or coloration), but getting the control of power / current reserve / voltage swing for the headphone to take benefit of / perform better. I won't call the increase of gain as 'improve version', as setting higher gain introduce more potential for distortion, which is the first thing to avoid in any amping. Just because It is done on request doesn't mean it is actually better. To me, the only thing that really needs to be improved is its transparency, a gain switch will be very nice but it is not the priority since the majority of IEM / earbud out there doesn't really need that much power to begin with.
While I agree an amp can do what you say and the E7 can apparently do that to a degree, the primary function of an amp is amplification. That means to amplify the power and signal of the source. Conditioning the signal is a secondary benefit and tends toward being a line conditioner more than an amplifier. If you can do both then that's ideal. The argument just doesn't hold IMO when the E7 used as a DAC has a higher gain than the HO. I'm sure this discrepancy is intentional in the design, and that's fine. I just don't think consumer expectations are in line with what you are defining as amplification. What about the ER4-S at 100ohms? You really want to tell them sorry your IEM wasn't designed for our amp?
Edited by Anaxilus - 7/29/10 at 11:34pm