Awesome news!
I *highly* recommend "In Service of the Duke", as that's a phenomenal price for this enormous book. It's a leather bound, heirloom-quality book, printed with high-quality glossy archival pages. It's a whopping 15.6 x 13.2 inches in size, and has full-color reproduction of the pages from an original manuscript with all of the combat imagery. It's the closest you'll get to having the actual manuscript in your collection.
"Secrets of German Medieval Swordsmanship" was Christian Tobler's first book on medieval fighting techniques, and while some of the information in it is outdated now (there are superior interpretations in his later books), it's still a good one to have in the collection and was one of the books that helped shape the modern WMA/HEMA community.
I'm going to pick up The Duellist's Companion and Deeds of Arms, since I don't have those.