I believe the Plymouth line by Smartpak comes in oversize, and the leather is quite nice for the price, around $70 IIRC. I like mine a lot, although have not used yet so can't speak to durability. But the leather is nicer than many $$$ bridles I've come across, I think.
I had very good luck with Bobby's for my tank of WB's head. Used it as a schooling bridle, but it oiled nicely enough I wasn't embarrassed to show him in it, either. Farm House carries Bobby's and can probably give you a guestimate of whether or not it will fit your big guy.
ETA--I also used that bridle on a draft cross who measured at 18h (she was a beast of a horse), and while yes I was approaching the last four holes or so, it still fit her in across the browband and such, and she looked fine.
Kincade is very stiff in my experience. Not the kind of leather that is pleasant to work with. I have heard good things about Plymouth, and I have had good experiences with Henri de Rivel; nice stuff for the price. Ovation bridles are also pretty nice, as are SmartPak Harwich bridles if you can stretch the budget by about $50 more. Also, look for nice used bridles at tack swaps, on ebay, etc. You may well find some nice bridles in nice condition under your budget.
I bought the full size SmartPak Plymouth Elite Dressage bridle for my big headed TB. The leather is nice, and for the most part, it fits him well. (I had to get an oversized brow band from justbridles.com)
I have a HK bridle and the leather is really good quality. If you check out the horse size Regal that is also for sale on eBay, you can see how nice that OS bridle will look once it is oiled and broken in. HK bridles are sold in my local tack stores, so I have looked at many of them up close. I ended up buying a used Aramas by HK event bridle and matching new reins to it from the tack store. It is classy.
A helmet saved my life.
2014 goal: learn to ride like TheHorseProblem, er, a barn rat!
Its funny, an HK was the first thing that came to mind when I saw your thread title. I picked up one on ebay (not sure about the model - it had a flash attachment I cut off) but it is super soft and amazing quality. Got it for $70 and it rivals my $400 ADT bridle in suppleness.
Another vote for Smartpak bridles. I have a 17H warmblood with a big head. He wears an over size halter, my full size bridle (different brand) was too small for him so I ordered the over size Harwich bridle. It was too big! I sent it back for a full. It is a really nice bridle and obviously very generous in sizing!