Got it. Very raw initial impressions, from a hifi noob:
Old setup: Laptop + AKG K550. Off the laptop's card, the K550s have a sound that feels spacious but not grand, analytical, a bit lacking in bass presence. You can hear everything but there's a distinct lack of punch to it, and the sound feels maybe a bit cold, clinical, controlled rather than emotional, warm and lively.
The initial listen (Laptop=>FiiO=>K550)
The first feeling listening to the E17K was claustrophobia. It felt like the previously spacious room was turned into a Japanese capsule hotel or something like that. A small closet with everything stuffed in my face. The bass was noticeably more forward, and I could make out a lot more details in the lower frequencies. It definitely felt like I'm not listening to just the music.
More listening after a night's sleep:
Things still feel like they're much closer, competing for less space, but the initial really congested feeling was probably just not used to the bass being this present. Bass still very much forward and sharp, distinct.
Tinkering with settings, upping the gain from 6dB to 12dB feels like the sound gets considerably more life and presence, and the feeling of congestion lets off some. It's a good sound but very different from the one without and does feel a bit tiring compared to listening without the FiiO.