a 7 would be more of the "air through the nose but still silent chuckle" i would think.
but the gasp plus lol would indicate some level of audible response, so that means at least an 8.
i suppose the voracity of the gasp would be the determining factor on if it rises to the level of a 9. personally i don't think it does but cnk is the judge on this one.
for reference:
http://tigerboard.com/boards/view.php?message=19491337