For my use - mostly at work with SENN HD560s headphones connected to a PC with software EQ - maybe the Q5K isn't the best choice. The 9038S or S9 may be the better choice. And the S9 seems to be the better choice with 3.5 and 2.5mm headphone jacks. Does that seem reasonable?
My mobile use is mostly with sports - skiing, hiking, weights, hill repeats, etc. I'm currently using old KSC75 earphones for that purpose. Today I connected my Q5k to the Koss earphones, and the EQ did help. BUT - I'm using bluetooth and an iPhone - not high quality audio. I could make a wired connection to my phone (I have the camera adapter), but for sport use it gets in the way. I'm trying to find a high audio quality solution for sports; even if I'm breathing hard I'd like to listen to good sound. I'm seeking better headphones (probably durable IEMs - thinking Aria's, but maybe something bluetooth [ugh]). So, I need to ask - is the Q5k a useful dac/amp for my sport audio needs? With IEMs and an ACC bluetooth connection, is EQ alone worth the price of the Q5K? I wish I had LDAC, but my family lives in an Apple world.