How can I make the best use of prime beef?
If I'm spending the money to get prime, aged beef, I'm going to cook it rare if I cook it at all. The more you cook it, the more flavor you're going to lose. In the restaurant business, it's not uncommon to slip you a substandard chunk of meat if you order the fillet and you order it well done. How would you know the difference between good and bad at that point?

Likewise a lot of additions. There is a place in town here that does an extraordinary fillet stuffed with goat cheese and cranberries, and one of the best I've ever tasted was covered with bearnaise and crabmeat, but, as a general rule, don't add a lot of extra flavors to high quality beef. The worst thing you can do is hide the taste, since that's what you're paying for.

Still, aside from the two that I mentioned, you can stuff with blue cheese, make beef wellington, or make beef stroganoff (Link is to James Beards version, which, imho, is the best); quality of meat is huge in stroganoff. I'd only use fillet there, or some other very lean cut. Saved the marbled stuff for the grill.