Here's what you would be doing in that audio chain: Use the DSS to convert the Dolby Digital Live 7.1 into Dolby Headphone, use the DSS' DAC to convert to analog, the ADC in the product you tried to link (I only see a blank page) converts analog back to digital, and then the Mojo converts digital back to analog. To get 7.1 surround converted to Dolby Headphone, you HAVE to put the DSS at the front of the audio chain, right after your source (I assume a game console, like the PS4 or XBO?). Even with a "theoretically perfect" ADC your final quality would be limited by the DSS' DAC before it even gets to the Mojo's DAC. And no ADC is perfect, every step of conversion is lossy. So, what @Yethal and I are trying to say is that you can never get better audio than what the DSS limits it to at the DAC stage. To power your 300 Ω Sennheisers, you might as well focus on getting a good, self-powered, low distortion amplifier, which CAN improve the performance even with the DSS in the signal chain.