The surface pro 2 is a good way to go, make sure you are not getting something with Windows RT.
Your easier solution is an ultrabook, such as the ASUS Taichi21; I have one, and can use it in tablet or laptop mode, and do so with Cubase and Ableton often.
There are other ultrabooks which give you the tablet and laptop functionality, as well, and are powerful enough for even complex audio work.