Yep; unless you need SAS support I would recommend onboard SATA first.
OP, I have the same HBA card as you, it gets toasty even just idling, and even hotter once you throw a load onto it. I measured ~10W power use just idling (no drives attached to HBA). I almost guarantee using onboard SATA will be more power efficient.
Even better, is if you can physically remove the HBA card until you need it.