Dude, the Q5 has no interface, you can't run anything on it, it is a hardware device. How would you install and interact with an equalizer through the Q5? I have no idea what you mean. It is not a DAP. Are you suggesting that built into the Q5 would be an equalizer that is exposed to the different possibly sources? I am not saying that is impossible (maybe it is) but it is certainly not common for such a device and I don't think that FiiO suggests the Q5 has this ability. And it is not a DAP at all, it is a hardware amp/DAC and it relies on a properly featured source.
I realise that the ES100 has built in hardware equalization ability, but the Q5 does not and I would personally prefer the flexibility of a software based eq, but I guess if people want this, perhaps it is a feature that FiiO will put into a future product. Sorry for misunderstanding your intent, my bad.
I do realize that the way the EQ is implemented in the ES100 allows for a great deal of flexibility so that kind of renders my point moot. Maybe I will become a fan of built in hardware equalizers.