I'm about to start my 3rd year in physics at Oxford, and I want to do a theory Phd eventually. Unfortunately though, I don't think that the fourth year at Oxford is very good for aspiring theoreticians (there are no courses in string theory, QFT etc. the particle physics option is experimentally based, and the theoretical option is very strange, doing things like classical field theory and statistical mechanics). I'm currently considering going somewhere better to do my 4th year. The immediate possibilities are and MSc at Durham or Imperial, part 3 of the maths tripos at Cambridge, or going abroad to America. Does anyone know what the best path for me to take is? Also, if I was to study for a year abroad and get all of the normal grants available, approximately how much would it cost for the year?