There is no denying T6500 being the better chips c/o with T4200. Just does it worth upgrading for $800HKD? Can you tell the difference in everyday use? I'd say it'd be money well spent if it goes to more ram, better spec other than the CPU.....Last time I checked, Dell is asking for a mere $35 USD for a somewhat similar upgrade from 4200 to 6400 in the States for their notebook. Go figure