Good! Nice to see York finally getting on the ball with their prices. $400 for 2 Hyperions is a decent buy. The focal lengths you chose are spot on the most useful ones for the 12" Dob. I say go for it!
I would not bother using the EPs without the barlow bit, because they will perform poorly in the 12" Dob. But you may be interested that Baader are coming out with focal length tuning rings that you can screw between the built in barlow lens and the rest of the EP to reduce the focal length. The 13mm could be turned into an 11 or 9mm, for example. For me, the most useful deep sky FL for the 12" Dob is around 10mm, so these rings would be handy.
The Hyperions are very similar to the Stratus which work very well in fast scopes like dobs. I've used both the 8 and 13mm Stratus and have been very happy with them. In fact I kept my 13mm Stratus over a 13mm T6 Nagler.
A German company does put their name on them but afaik they are made where just about everything else is. But it's performance that matters not where it's from. 
