slevinProbably too late now, but the main differences are:
S2 - weaker headphone amp, MQA/Roon support, remote included, smaller
DX7S - stronger headphone amp, higher output impedance, balanced HP out, XLR out, AES input
So really you'd have to decide what features matter to you since they're similar in price. Personally, I think you're getting more with the DX7S. If you don't care about XLR out, the Topping DX3 Pro might fit the bill for you for much cheaper. If you're willing to go separate units, SMSL SU-8 + JDS Atom might be a nice combo for less than either of the combo units.