On another note though, is there a particular good stage for getting the 555km trophy? This is really starting to bug me.
The best stage that I can think of is an Awakening Mission that take place in the Wasteland, Forest, or City. So it's the Awakening Mission for Ryuki, Faiz, Blade, Hibiki, Den-O, Kiva, Decade, W, and OOO. Just play the stage like normal until the stage become clear, after beating all the secondary Rider but before fighting the main one. Now the stage are pretty much empty and there's no time limit with the exception of the Mission time. Just drive mindlessly with your bike while avoiding the boss location (Temple for the forest, upper-left side of the map for the city, and the top of the mountain for the wasteland).