I believe you can nab dfk 1.51 for a couple dollars on XBL marketplace, but imo the best part of the entire package is the arrange mode that Yagawa worked on which is exclusive to the disc-based J360 version. If you have a J360 I'd suggest grabbing the disc-based version.
any LE I've ever owned (for cave that's only DFK and Mushihimesama HD) hasn't been worth the money tbh. It's nice for the different art/box, but kinda worthless if you're not a collector. They usually come with a soundtrack cd that I never open, and the DLC code.
You can get the DFK arrange mode with the Black Label DLC. The exclusive mode for the disc version is the DFK/Ketsui crossover.