What would you gain by going to 700c wheels on the bike? It seems like a money pit idea to me. If you just want to make the bike more efficient for commuting, go w/ 26" slicks. If you're set on the idea of 700c wheels, get a new bike/frame.

BTW, I had an old Rockhopper that I turned into a nice, light singlespeed. I bought a Cross Check for commuting and road riding.

baker