there isnt an "ecom" course at unsw. what u can do is a BCom in information systems. commerce has a very very good scope atm, but not IT. so if ure really interested in the infosys course, maybe u should be looking to do a second major in accounting/actuarial/finance ....
and if ure thinking of going on exchange, especially to europe or the americas. they dont use the WAM policy, just the GPA.
on a side note, i realised that Univ of Illonois, which i'm thinking of going to next yr, calculates the GPA out of 4, not 6 ...