Yes, the service packs are cumulative.
Great news! Can the KA be updated to reflect that? (since comments are not available for this KA, people who look at it will not see this question & answer, so updating the KA is the only way to go in order to share the good news)
LOL! Yeah I wanted to comment on the KA but was not able to (almost turned on comments but that would be a bad use of my powers) ]:-)