The pickups in the 513 are the exact reason I have stayed away from this model. The 513 came very close to being my first PRS. A shop that I bought a ton of gear from had one in a finish that I really wanted, my first PRS, a CU22 is actually in this finish. I drove to the shop, about an hour drive, and played the guitar. It was supposed to be a hum free single coil sound. The one I played had a lot of hum in it. I am sure it was a combination of the amp and power along with the single coil setting on the guitar. That really turned me off. I bought a Hamer that day. I just couldn't buy the 513 when I had absolutely no way to change the pickups in it and I didn't like what I heard.
You would probably be better off selling the guitar and buying something else you like. If you have to heavily modify it, you will kill the value if you ever decide to sell it.