I'm currently looking for a saddle for my TB as well (in a similar price range too), and it sounds like he might have a build not too unlike yours: High withers, narrower build, but big shoulders.
I can tell you what didn't work: My old Bates Elevation. I finally had to sell it.. just didn't have enough wither clearance. I had to use a super puffy half pad, and after a while I couldn't handle putting a bandaid on the problem anymore. Bates and Collegiates have the same trees, so I'm excluding Collegiates from my search. Also, I tried some old (and I mean OLD) Crosby saddles on him, and they were the worst fit of all. I was surprised because I have heard old Crosby saddles could be good for TBs. Nope, not mine. I also tried a Circuit on mine over the summer, and it also didn't offer enough clearance for my taste.
I'm ordering an M. Toulouse test ride saddle next week. I've heard mixed reviews about them regarding TBs, so I figure it couldn't hurt! If that doesn't work, I will probably try a Beval next. And if that fails.... then I don't know.