Seeking accessible music player: necessary for business purposes!

Hello everyone, are there any suggestions for an accessible music player that supports many audio formats and does the following:
1) plays files directly from Dropbox without first downloading them to the iPhone or iPad;
2) allows bookmarks to be set while a track is playing;
3) remembers the last position of a file before closing, and resumes from that position after relaunch?
I am willing to use paid apps, but only if the features listed above are present. I require such an app for business purposes and greatly appreciate any suggestions this community can offer.