You say you don't want to spend too much money and I perfectly understand that, Ala13_Kokakolo.
The part I don't get about this: If your resources are limited or you just don't want to spend too much money on new hardware, why you are going to buy yourself hardware BEFORE you even know how BoB runs on your computer?
Even if the minimum requirements and optimum requirements are released, which would need a pretty advanced beta to know, how can you be sure you upgraded the right parts without having the chance to compare the importance of different components for the game?