Can I inject USB Power Delivery through a hub or some other device?
Solution 1:
If the hub has its own power-supply it will take of the PD by itself.
If it doesn't have a power-supply it will just pass on whatever is coming from the computer and (possibly) even remove the PD if the computer supplied it.
Use of PD is independent of the actual USB data-signal on the same connector so you won't need that AUX cable. (And with the AUX cable you won't get any benefit of the build-in DAC in the speakers anyway. AUX only supports analog signal.)