I'm not sure which one I prefer:
1. Every dependent entity has a sustaining cause. (Premise)
2. Either there is an independent first cause, or the regress of dependent sustaining causes is infinite. (Implied by 1)
3. The regress of dependent sustaining causes cannot be infinite. (Premise)
4. Therefore, an independent first cause exists. (From 2 and 3)
This version of the ACA does not require the PSR, but only supposes that there are, in fact, some entities that are causally dependent on others.