I think Harper goes well with Mason. They're both last names that have seen big popularity surges in recent years, so they have a similar feeling.
Here is Harper's trend line in Ohio:
By contrast, Mason spent 14 years (1995-2009) climbing through the top 100 a little bit at a time before breaking into the top 10 (it was #1 in 2011). So Harper is trending much, much faster than Mason. It may not be top-10 in 2012, but it seems headed that way within the next 3 years.