I third or fourth the recommendation to go with a 10-weight if you already have an 8. Fish an intermediate on the 8, and you can fish surface down to about 4-6' with ease. Put a 350-450 grain sinking line on the 10 and you can throw big flies, fight the wind and also fish heavy sinking lines if you want to fish down deep. Some guys even like to fish the heavy lines over the sand flats as it gets their fly to the bottom quick.
I have a Sage Xi2-10 weight, but for the $$ and the amount of use you are going to give it, I'd go with a lower end rod. I don't feel that the upper $$ rods justify the sometimes 2x increase in price over whats available on the market today.