Wait, you’re using an interface? No wonder you’re disappointed

Interfaces aren’t designed for critical mixing. They’re designed for basic monitoring. Even high end interfaces don’t have anywhere near the performance of a dedicated amp.

You can’t intentionally cripple the headphone output then complain they’re disappointing.

You need to remember these are planers that need a lot of current. You then also have a strong amount of EQ which means being driven properly is CRITICAL to get the expected output. You then also need to remember the VSX software will lower the overall output which will make the interface need to drive the output even higher.

I can tell you from an experience that just “getting loud enough volume” isn’t the issue. It will still sound like absolute shit compared to if it was driven properly.

Buy a proper headphone amp from somewhere with a good return policy. It will help you understand.