Well, many of us actually don’t care about audibly irrelevant differences, or computer gobbledegook such as USB class unless there’s an audible performance difference or usability improvement in this application. Even for those who do like to chase numbers, if a headphone DAC/amp combo does not provide EQ then none of the EE specs matter because fidelity is not there regardless. An analog headphone amp downstream from a processor-DAC is a higher fidelity option. I’d like to see more useful integrated desktop headphone products, because there’s no reason for DAC/amps to fail to implement useful EQ. This is a giant hole in the market, while functionally inadequate stuff with pretty engineering data proliferates.
As for Quedlix vs miniDSP Flex, both are fine in concept for this application generally, but there are important differences. The “wrong” refers to time more than anything else - Quedlix was on the market first, so a subsequent product cannot be said to have changed the game. Between them, Quedlix is 20% the price, much smaller, has crossfeed, and has more presets with an iOS UI to select between them. miniDSP has higher output, balanced outputs (I don’t think the “balanced” Quedlix output can drive normal balanced inputs), and better measurements. The main real differences between miniDSP Flex and the older 2x4HD for this application are Bluetooth (good), and a second volume knob that provides direct access to presets.
Personally, I find UI more important than “performance” as long as thresholds are met. I used to use a miniDSP 2x4HD as processor-DAC in front of an amp with crossfeed. But it was a PITA to switch profiles for different headphones. Quedlix with a higher gain amp is a more user friendly setup.
Quite the opposite. The central insight from here in the headphone space is that they all need EQ.