I've found VPlayer Pro, plays MKV but doesn't show embedded subtitles. So I got MoboPlayer. That showed the subtitles but after playing part of one video, quitting then coming back to the video later, there's no audio.
What else is there that will work and stay working? An added benefit would be the capability of changing the subtitle font size. They're just text files, not images like in VOBs.
Does the stock player on the Epic play mkv files? I have the Galaxy Tab, and the stock player plays mkv's without a hitch, but will not display the subtitles embedded in the mkv file. But if you put an srt file in the same directory with the same name (apart from the extension), it will display those subtitles. I've watched a couple of movies like that, and it will pick up where you left off and all that good stuff.
There are a few Android Tablets support import of external subtitle e.g. Galaxy Tab. I have tested MP4, AVI, MKV, WMV files; both the original player and mVideo player support them well. When playing back the videos, name the subtitle file same as the video file and put them in the same folder, then you will see a video with subtitle.