[ProtegeManiac]

But saw the Fiio e12a amp on sale. I mainly use IEM but I also have some low impedance headphones like the vmoda m100 and akg k7xx (62 ohm), sensitive stuff that'll have hissing issues that's why I avoided the e12 regular black version.

Excuse if I might misinterpret stuff. I checked and the k7xx that I have says it has 62 ohm, Sensitivity: 105 dB/V.

The K7XX does not have high sensitivity and that is efficiency. They're essentially the same thing, but convert those figures to sensitivity and you get somewhere around 93dB/1mW.

Other things you have to consider: given input signal (to the amp) voltage, gain, etc, it's not literally 93dB as soon as you twist that knob from zero; power input to dB output is logarithmic so roughly for every 3dB increase you need to double the input power; distortion and noise levels also need to be kept below audibility regardless of how much power you're making the amp push out (otherwise even if you're not hitting clipping you're still getting distortion or noise).

It's not as sensitive as the others but with my pc soundcard on a 64+ impedance, I can hear some hiss. Though I do find it odd that it only hisses when I play videos but not while playing music files.

That can be due to how video gets your graphics card running and that's where the interference is coming from.

I like my bass hard hitting, but also enjoy all kinds of music, classical, oldies, whatever. Would the amp help boost the bass and increase sound quality or should I just fiddle with the EQ?

My Meier Cantate.2 had slamming bass on the K701 and K702, mostly because it has a lot of clean power. It gets loud so you get to the point where the bass is really loud, it doesn't distort, no noise that gets in the way of the music (especially the bass), and the output impedance is low so it doesn't EQ the sound.

Despite that some people still find that inadequate and very generally an amp like the Cavalli Liquid Carbon or Burson Soloist/Conductor are preferred by most.