http://www.drs2006.com/manuals/faq/plsasx.html gives info about pls and asx files in one place. But the pls files' titles are still not being reflected on Xmms, and the filenames are being shown. Probably since Xmms doesn't support Version 2 pls files? Maybe I have to tweak the server settings to not show the filenames?

Server being a relay automatically shows the origin server's title setting. If it is not a relay? Have to try out and see locally.