So true, twice as many as needed. We have Analog phone system which going to be deactivated, and will be placing a UC system in place.
I think I can prove that dual switches no matter how you spread across the voip will be more heat and power. not by much.
Tyen there is a limit on how many ports can be set to PoE+ typically only 24 on a 48 port switch.
Best Wishes