Edit posts, no bumping.
The P55, etc came out before the "3s". They don't natively have SATA III, USB3, or PCIe 3.0. I'm sure there are a few boards out there they have USB3 as an add on chip. Problem is if they are like SATA III they won't perform as well. My 840pro was bottlenecked pretty good on the add on SATA III chip.
Seeing as that system is dead, I'd get a whole new system. If it still works for you but you just want faster USB speeds for some reason, I'd get a PCIe add in card. Front USB 3.0 ports will work, and you'll gain a few ports in the back.