Look at PowerAmp, link to features below. There's a section on folders and a screenshot. See if this is ok for you.
I'll probably eventually try it since so many people use it but it gets mixed reviews on sound quality.
In addition to Rockbox I found an app called "Beam Player" whose main purpose is to play from folders so I may try that as well, although I have no idea about how it sounds. There is also one called "Folder Player" but recent reviews mention a problem with the latest update. (Has anyone tried either of these?)
"Poweramp can play songs from pre-selected Folders or from own Library": What I now think is happening is that what some players call "Folder" support means just that they can play from a folder (which is necessary for me) as opposed to playlist or some other way, NOT necessarily that it also ignores the tags on the songs INSIDE the folder, which I also need. I know Rockbox does this (at least on my old Clip Zip which disappeared) so I will see if the interface works on my phone. Again, really wish Neutron did this since it sounds so good. I may just end up getting another Clip Zip and SD card for my other pocket and save my phone battery.
Edited by tman1 - 2/18/14 at 2:25pm