I'd be interested in the answer you receive as I am also looking at buying
a Blanco Silgranit sink and would like to put in a soap dispenser.

We purchased the Avon model which has only 2 holes, but other models
such as the Vision 210, Vienna 210, Somerset 210 have lots of extra
punchouts (between 4 and 6 additional knock-outs) which would give you
pleny of room for the soap dispenser. Unfortunately we didn't have many
options for our purchase as we are trying to get our kitchen done before
X-mas so had to purchase an in-stock model.