Don't hardwire the seats. If you ever have to remove them, it becomes a Pita.
When I pull power seats from the wreckers, I clip the harness so that I get both male & female ends of the connectors.
The seats only need power & ground anyways. I ground the seats to one of the seat bolts with an end-ring.
The power can then be drawn via either into the proper location in the fuse box, or, what I did, was to tap into one of the non-used ports in the stereo's power distribution block, with an inline fuse after the D/block, before the seat's switch.