This depends on the sink that you are replacing and what kind of cut out you have. If you are looking to fit a sink that is larger than your existing one, it is possible that, if you enlarge the existing cut out, you could keep the existing countertop. Every situation is different so Bathroomware House recommends you consult with your cabinet maker before purchasing the new sink.
Laundry cabinets can be a simple solution to this problem as the trough is already in the cabinet and the unit is ready to go.