Well, if I understand you correctly (And I'm not sure I do ), "backup" DS games do NOT work with single card download play if they are the host. However, they work fine with multi-card play, as well as Wifi play. Yes you can play download play like that. He was using that and he had sonic rush( i think) but i didnt. So he did download play and we played. Maybe its not for all. Thanks for that guide Mooney, im gonna hop to it quick Also how much $ would that all run me??