The 513 is now no longer part of the PRS core series and basically replaced by the 509. I am not sure how the 'Rosewood' issue affects 'older' guitars that were made before this situation occurred or if it only affects 'new' guitars. I assume any 513 now would be from stock that haven't been sold or second-hand. That will limit you anyway on availability and potential opportunity to find one.
If its really clean' single coil tones you want, the 509 is perhaps the 'better' choice as it is built with 5 single coils - part of the naming is relating to its 5 pick-ups and the 09 part relates to the 09 variations in tone selection. Its got the 5 way switch but the middle position (middle single coil) is the same whether you split the neck/bridge or not but each of the other 4 options (B, B+M, M+N, N) can have either the Split or Humbucker therefore doubling the options.
This video shows a good range of the tones in 'recognisable' tunes so you get to hear the 'single coil' in use.
As you can see it has a lot of potential to fulfil multiple genres - the only thing it can't offer is the Bridge/Neck Humbucker combo.
I do find the 509 to be much closer to the 'single' coil sounds you would expect from a strat/tele. The 594 is a great guitar but I do think its more of a Vintage Les Paul first and foremost with the added bonus of splitting the coils to give it a bit more versatility and options. Its a quality split too as it doesn't lose much in volume either but I think the Single coil sound is more like a thinner version of the humbucker tones it offers. I am not criticising it as it sounds fantastic but I don't think it sounds like a traditional Single coil.
You may want to skip to around the 6min point to hear the guitar with Humbucker and Split tones.
Anyway, that's my opinion and hope this helps you to come to your own opinion.