For subtitles you can use DVD Flick (free) to convert to DVD. There's certain types of subtitles that Flick can't use, so either you need to locate compatible subtitle files or use a.n.other program. I also use ConvertxtoDVD but that's not free; there's loads of free programs but i can't help you with that, they all look like spam to me; i also don't ever bother with altering the sound on AVI files, it's always better to get another copy of the AVI
ConvertX can increase the volume ( look under the Audio tab) and handles all subs quite well with lots of size/font/placement/color options.
