I was advise against the upgrade that you wish to do. I would go as far as to say that it would be a downgrade. Look at the names, you have a MacBook Pro and you are thinking of buying a simple MacBook. The MacBook still only has two cores, the same as your machine has and only runs 10% faster.
OK, your model doesn't have the turbo boost, but to be honest, it is not worth it, anyway. It only works on a lightly loaded Mac CPU - on a more heavily loaded CPU, it causes the CPU is warm up and once it reaches a critical temperature, it turns itself off. So while the marketing-speak would lead you to think that it will hurry along CPU intensive tasks, such as running Mathematica and MATLAB, the truth of the matter is that it will not. It will only really have use on a truly single-threaded process, and not many of those exist in the examples you give.
The cheapest option, as suggested by IconDaemon would indeed be a RAM upgrade, your MacBook Pro can actually take 8GB. That would not only give you a significant performance boost, as there would be less swap/disk activity, but it would also increase your multi-tasking ability, both in speed and number of simultaneous applications. Add to that an SSD, and it will not only boot faster, applications launch quicker, but switching between apps could be quicker, and disk intensive applications, such as Photoshop would be arguably quicker. Pretty much as IconDaemon has already said.
However, if you really want a new machine, I will add that if I were you I would go for a second hand (cheaper than new) quad-core i7, such as those from (late) 2011. You could get a 2.5GHz Quad Core i7 17" MacBook Pro for the price of the new MacBook that you have your eyes on. Blisteringly fast.