I hate to cloud the issue but, with spey profile lines, I would be wary of going a line size up. For most spey lines in medium to long heads I often find that a rod performs better by going a size down. However, as I have not tried the Grey's rod with the Snowbee lines I cannot comment on that particular set up.
A lot of spey lines, when you weigh them are too heavy for the rods for which they are designed. There has been a lot of discussion on this forum about this subject. Here is one example that shows the new Spey Line Standards from the states - http://flyfishingforum.com/flytalk/index.htm