Actually, come to think of it, I believe all I need is
this. That flip-top is designed for the Slimline PS2, and I imagine it allows me to swap the discs without resetting the system, which I believe is what would happen if I were to get just the Magic Swap disc without the flip-top, since hitting the open button on the slim tends to bork everything up.
And I found Haunted Castle for $35, which is still pricey, but eh, whatever. Since it's Japanese I imagine it emulates one of the much easier Japanese versions. Shame the soundtrack CD isn't as bassy as some Konami collection CD, according to Kurt, but oh well, still kind of cool to have I guess. I wish it were better, though, since the music is by FAR the best part about this game.
Soon I'll have to import me some beatmania games since I own two controllers.