I own this same radio wish i would have got something better i really just hook my ipod up to it and listen to my music because it doesnt play cd's correctly everytime i put a music cd in there it makes some crazy noise like its scratching the cd then ejects it saying error or something but it plays dvd's fine.
But anyway to answer your questions....no you can't complete turn off the subs you can only turn them down
For the six channel surround that can only be used when watching dvd's that contain surround sound material