Smith Worthington is what I have for my "wide load" (and wide shouldered!) Morgan gelding. Fits him very nicely. He's in a wide, but if you send the saddle to them they can refit their saddles to your horse for something like $100. Including, I think, some tree adjustment.
Edit: I took a look on Ebay and saw this one (not my saddle/ad!) http://www.ebay.com/itm/17-5-Smith-W...item1e784a334b
I've ridden in that model before, and find they fit a little snug - I usually take a 16.5 seat, and felt just fine in a 17 in this model of saddle.
Have you had a fitter out? I have a friend who has a whisky barrel shaped gelding and was trying to fit him into all sorts of wide tree jumping saddles. It turned out that while he was very wide in the barrel and around the ribs he was a medium on the top of his back by his shoulders and fit nicely in a medium tree saddle.
I second the Smith Worthington recomendation. If not so interested in the Ebay listing, visit their website for many options. I bought one from them that fits my wide shouldered, flat backed QH very well. Their customer service can't be beat and they have a fabulous trial policy.
II'll second the recommendation of working with a good fitter. Many of the Arabs and crosses I fit need a hoop (aka dome, Freedom head or FWB) tree, which is broader across the top of the pommel arch and works well for the "propane tank" builds. Most of the UK-made saddles are available with that option: Loxley/Bliss, Black Country, Frank Baines, Ideal, Albion, etc., and most of their jump saddles can be made on that type tree. If your budget won't cover the cost of one of those, the Duetts are a great option for the broader horses and offer very good value for the money.
If you don't have a local fitter, or one who's familiar with the needs of the broader horses, you can work remotely through templates and photos with shops that have experience doing long-distance fitting. Equestrian Imports and Panther Run Saddlery both fall into that category.
On the Duett - I haven't ridden in that model, but did try another model for my boy. The saddles do work well for flat backs, but I couldn't deal with with the twist - it was too wide for me personally.
Someone else may know more about this, but I think that they run wider than other brands with the same measurement because of the hoop shape. So, a 34 in Stubben for example, will be narrower than the Duett 34.
I missed out o the Smith Worrington, but may keep my eye out in case it is relisted. It is hard to find decent wide saddles and I don't mind having extra saddles sitting around for future lesson horses if it is a good deal, in particular an AP type saddle which I prefer for lessons.
RIght now I am just keeping an eye on a good deal, but if nothing comes up I will look at getting something through a fitter.