In principle, any ADC would do. However you have to be aware of the performance limits of the ADC. I can‘t imagine a cheap mixer to be all that useful for measuring any but the worst devices out there. If the performance of the measured device and the ADC are closer than 10dB, the THD+N of the ADC will contribute a significant part of the total measured amount, so you‘ll have to calculate that out. It would be easy to establish a baseline with a known good DAC.