I have a Bob Marshall and LOVE it! Very comfy, great quality.
Other good brands that have western models include Ansur, Freeform, Sensation, Barefoot, and Black Forest. The last two are the most affordable. I have an English version of the Black Forest and it's nice quality for the price.
Stay AWAY from Hilason, Sydney Saddleworks, Maya, and any no-name or cheap eBay
Just keep in mind that with any treeless saddle you will need to get a substantial saddle pad. I use a Skito Saddle pad
with mine, the full treeless version. Skito pads are one of the most popular for treeless saddles. Other popular pads include Equipedic, Haf, Saddle Right, and Supracor.