Well, It seems you already have spent your budget in headphones!
I can suggest you a DAC+amp combo such as the ONIX DAC 25A or the AudioGD NFB-12 or something like that. They do support USB 24/96, even if not asynchronously.
A cheap DAC featuring asynchronous 24/96 USB technology is the Arcam rDAC. It also playbacks 88.2 files through USB, and 176.4 and 192KHz files through coaxial.
Then the Schiit Bifrost, very well-regarded here,...