Hi and welcome!
You certainly are in the right place here and we are glad to help mate, tis what we do around here.
What you are asking for is pretty darn insane I have to say, a 25" 7 string which ranges from the Beatles to prog metal. Wow xD
One question I have is that you say the PRS has "high treble". Do you mean acousticly or through the amp?
Now for what you want three pubs immediatly spring to my mind: Mule, Abraxas and Rebel Yell, with the Mule being my fav for you.
The Mule is a classic vintage PU. A perfect 59 PAF pup. A very balanced and open sound in the bridge, classic feel. Perfect for the old school side of your playing. However, since BKPs are insane, this thing can do much more. Got a nice amp and a proper pedal? Rock? No issue. Old school metal? BKP founder Tim Mills uses one in a Ozzy cover band. Need more still? Have a look here, a Vik guitar with a Mule bridge and a Manhattan (a P90 voiced for jazz) in the neck.
http://youtu.be/g-xQJOu9mN8Enough said? Good ;)
The neck is also just as great, being a nice warm neck sound with amazing cleans which can also do modern leads if you want.
Amazingly versatile set if the rest of your gear fits it.
The Abraxas is basecally a hotter version of the Mule. If you think you like the mule but need more power and hotness this is a good ticket.
The Rebell Yell is another thing, a modern take on a vintage tone. Brightest of the three, more modern oriented, but able to go for the vintage stuff too if you get a more vintage neck PU like the Mule or something. Just wrote up a long review for it:
https://bareknucklepickups.co.uk/forum/index.php?topic=30392.0Also have a look here
https://bareknucklepickups.co.uk/forum/index.php?topic=30219.0 for even more info on Pubs we might recommend.
Ask anything you like too, we are all Flanders here or some overly frieldy guy who is really forthcoming but just waiting to murder you in a gruesome manner to skinn you and wear you to impress mommy who has long been dead after a terrible car accident we were at fault for as we ripped the cats jaws appart in the backseatcausewewereangrywewereexpelledfromtheschoolduetoanincidentwherewepushedameankidinthepoolwhocouldnotswimandwejustwantedtoseehisfeebleexistenceendinasilentscreamseingthelastsignsoflifeblubberupasdaddydidbackatthesummerhousewhenhetriedtosaveuswhenwewentintothelakealthoughehtoldusnottobutwewouldnotlistenwewouldnotlistenwewouldnotlistenwewouldnotlistenwewouldnotlistenwewouldnotlistenwewouldnotlistenwewouldnotlistenordidwelisten....
Ah that felt good.
Cheers mate!