@TylersEclectic has a good idea here. At $399, the iFi xDSD has a line-out mode that will drive any proper AUX input. It also has the power to do a good job with the Sennheiser HD-650s and even my relatively power-hungry Hifiman HE-560 planar-magnetics.
You’ll already be familiar with operations, size is plenty compact. The next step up, the Micro may break your budget, size, and possibly thermal requirements.
I did a review of my xDSD here iFi Audio xDSD