I have a Brent Mason, and I've tried a couple of 513's, not in a while, though. Considering it's been years since I tried a 513, I'll try to remember what I didn't like about it. As I recall, it had a solid rosewood neck, which from my experience with rosewood Teles--I had one for a while--tends to darken the tone a bit, and that was my recollection of the 513. A later one that I tried (maple neck, maybe?) seemed like it was a little brighter than the rosewood-necked one, but still not where I needed it (I'm a Tele player for the most part). My take on PRS's for years was "Nice, but not really my thing...", until they came up with, first, the DC3, which I loved; almost bought one--but by that time I knew the Brent Mason was coming out. Paul actually showed me a pic on his phone of Brent playing a prototype, so I decided to wait until the production model was available. I got the Brent Mason, and it's very cool. Does it sound like a Strat or a Tele? Not exactly, but it'll come close, and the humbucker sounds are more to my taste than the ones on the 513. The neck pickup on the Brent Mason in particular gets the best jazz tone I've ever gotten out of a solidbody. I still wouldn't mind having a nice 513, though!
Another thing you might consider is trying to find a 305; that's the closest I've seen in a PRS to sounding like a really good Strat (and plays better than most Strats). But those won't do the humbucker sounds, and they've been discontinued anyway.