Well, you can warp back to the entrance when you get to lower levels and then skip around. I've gotten all of the shards except for the last one. I'm trying to figure out how to kill the last boss. The 100 million is actually pretty easy to get if you kill the robot guys on level 12. Catch them off guard and then go 6way harmony ftw.
BTW, if anyone has a strategy for the last boss in Unison, I'd appreciate hearing it.