I got Thornhill Vienna (it's under $1000 new) and love it. Their Klasse (little over $1000) was even better, but not a good enough fit. :( I absolutely love Black Country Eloquence, but they are close to $3K and still expensive even used ones. M Toulouse also has some nice dressage saddle (tried it, wasn't a good fit for my horses, but comfortable saddle).
BTW, if you feel comfy in 17.5 A/P, I'd look for the same size for dressage one.
"Life isn't about waiting for the storm to pass: it's about learning to dance in the rain..."
"When we are no longer able to change a situation - we are challenged to change ourselves."
"How people treat you is their karma; how you react is yours."