I would go with an AP saddle, either VSS or VSD (Dressage tendency). The APs will be the most comfortable for you. You'll want to go 1.5-2" bigger than your western saddle. Most horses that take QH or Full QH bars will need a Wide to X-Wide tree. Horses that take Semi-QH bars will need a medium to medium-wide tree.
I would look at used Stubbens, Courbettes, Crosbys, Collegiates, or antying else that is made in Europe. If you want to look at synthetic, check out Thorowgood or Wintec. Those are the two best synthetic brands.
Do NOT buy any No-Name saddles, Kincaids, Granada, Silver Fox, or anything else that just says "Imported". You want to be careful with Argentine saddles too as their quality can vary widely; some are fine and others are total POS.