Enom handles .de domains and has excellent, solid, geographically distributed DNS and all the other features you need, including paypal.

Their retail prices for domains are high, but if you have 50 domains, you can do a bulk deal with them that's about $15/domain for .de.

If you don't have 50 domains, I can set up a reseller account under our master account that would be about the same price, and you would have complete control of and access to everything. There are a couple of adult webmasters I've done that for.

Enom is one of the largest registrars around and, so far, I've had great luck working with them.