What Macbook Pro?

I have the money to buy a 17" 2.6 GHZ, however i would rather have the smaller one (15") due to protability. For $2200 I can get a 2.2 GHZ processor for an extra 600 I can get 2.4 plus an extra 40 gb harddrive and for an extra 775 i can get the 2.6 GHZ processor. Which one should i get i plan on doing CAD a bit of Graphics regular school work, maybe a but of gaming (not hard core though) and some internet and other basic functions.