hi,
i was also was about to ask that same question on the forum but eventually i've found an alternative to increase volume on the converted video. what i did, before converting the file is that i made a .wav of the entire video by using a audio converter and setting it to 4800 instead of the standard 1411. once you have that, go to the advance settings and select "insert wav if not enough... " then just add the audio file to the conversion. if your going to a dvd rip, just make a wav file of the avi. hope this helps in some way. it worked for me.
but of course, your video will increase a bit.