Great choice in luthier, I can't recommend Dylan enough!
The Atlantean was designed to be as balanced as possible, it's a really amazing instrument to play standing up. That'd be my recommendation, especially since you're going for a longer scale.
Cost is going to vary alot depending on the intricacy of the artwork (basically just how long it will take him to do), and the hardware specs.
If it's of any help, both my guitars came out around the £1800 mark.
Why not fill out the custom quote form on the site, you'll get a much better idea of what you're looking at in terms of cost.
WHat doe sthe Valkenbyrd look like? Can't see it on their site.
Dylan hasn't built one yet, but you can see the template in this promo video he did:
http://vimeo.com/5530740He is building one right now, though as it's for stock the customer orders are taking priority so it might be a little while before it's done. Should be pretty epic though, it's got a stunning burl maple top I almost chose for my 6-string.