The addition of WoodyOPL should probably be applied after the modification to AdPlug that I've posted.
WoodyOPL is the default emulator in adplay-unix, after applying all patches. I don't have a problem if one prefers to not change this default.
For SDL 2.0, AM_PATH_SDL was replaced with EXULT_CHECK_SDL from Exult (with wjp's blessing), albeit with a minor change for MinGW (tested with another app). configure.ac should also have an additional log message reporting the detected SDL version (although this may be unnecessary).
A new --with-sdl option was added to 'configure' as a consequence, letting you select between SDL 1.2 and 2.0 (if development files for both are available).
I've observed sound crackles at times, usually reproduced with WoodyOPL, but also with Ken's emu and possibly Satoh's as well. I suspect this may be an ALSA player related issue, though, so the SDL player might be a better choice.
Surround mode is (still) not compatible with kemu, but hopefully it is with wemu. In addition, wemu should be compatible with mono and stereo streams, using either 8-bit or 16-bit sample quality.
Some notes: