Well, see. The thing about research is that if you don´t really know how to do it properly, or have the prerequisite knowledge, it is useless. I see how this might be offensive, so I will not say "no offence". I will however say this: My main intention is not to offend you.
Now, if you could tell us what you want and/or need, I for one, will be happy to help you.
SC2 and Diablo III is not the most demanding, hardware-wise, but I am going to assume that you want to play these games because you enjoyed SC and Diablo 2 when you were younger.
As did I. Thing is, there will be other games like these you are going to want to play. With your budget, and since you are able to start a thread on this forum, you do meet the...