I am going to study architecture in London from September, and now i am considering what computer to buy, my budged is quite limited. I need portability and performance, as i will need work with such programs as autocad and etc. and also i would like to cary it around most of the time. Need an advice. Macbook pro 13 inch 2011 + External monitor. or Ipad + imac 21.5'? First option would be less expensive, but imac would give me extra performance. What do you think?