Top 10 in canada, no much chances. I do not the situation for Singapore schools. So much candidates have the similar background.
In my opinion, you'd better improve your GMAT to at least 680. bottom line for Chinese mailand candidates. better over 700. Then you got the ticket to enter into the circus to play.
if u have very strong W/E,then ur GMAT does not matter too much. possibly u can have a try and at the same time prepare for reapply next year. even if u fail this year,u will benefit from this experience and improve ur 2004 application.
According to my knowledge, Canada BS pay seriously attention to your GMAT, and even its tuitions(2 years) are not cheap compare with Europe(normally 1 year)!