I spent a lot of time thinking about this; I think it is critical to really understand what you want the bike to do and where you will ride it as there are many options. When I moved to a very urban part of Seattle (description probably redundant) I found really crappy roads, really bad drivers and really steep short hills. Even with 32s my road bikes seemed fragile for the roads - do you dodge the crevasse in the road at the expense of having to move into traffic, do you bunny hop it, do you bend your rim or break a wheel going over it? At the same time we have some really nice forested parks with gravel roads and short sections of mostly smooth single track that can be ridden as a nice respite from the road. And if you go out of the city we have some really long gravel rails to trails conversion.
For an average gravel road I would just take my lugged Kirk with 28-32 tires. But I wanted something more burly for the varied riding in the City. I also wanted something that could be used for commuting if that became a need in the future, and something that wasn't so expensive that I'd be uncomfortable locking it up outside a store etc.
What I settled on was a Singular Gryphon. It is a drop bar specific 29inch mtn bike frame. Had the Singular Peregrine been in stock I probably would have chosen that but the Gryphon works well; just fewer braze-ons and a bit of an ugly duckling when you add fenders etc. to a steeply sloping top tube. Both are designed around 29' wheels. They have an eccentric bottom bracket so you can easily switch between ss, geared or internal hub. Both are designed for disc brakes, which I made a design requirement for our steep/wet roads.
I am very happy with the bike. It rides very nicely. I sit high - much higher than on my road bike, but can stilly achieve a road position. It eats up bad pavement with aplomb. I've added a rear rack and have a dyno hub front wheel to power front and rear lights for commuting and night riding; accessories that are easily removed if I want to use it for extended riding on trails this summer. And the cost was reasonable. Pix are here at post #33:
http://forums.thepaceline.net/showth...gryphon&page=3
If I lived in a more rural area and wanted a gravel bike I would have looked hard at the Boulder Bikes 650Bs, the Rawland offerings or the Salsa Vaya, particulalry the new s&s coupled stainless vaya - a really versatile option (the ti warbird is a nice looking bike as well, but lacks eyelets for fenders, rack etc.).
Good luck, I think these bikes are a fun project and there are lots of options out there.