Thanks for all this guys, I think in the end I might go for a new laptop instead. My dad might buy me a new laptop since we might be moving to a cheaper area. We've discussed it and I think I get more benefits if we move. I have to take a bus every day to school but I'm considering that as a positive because I get experience with public transport. I'd prefer to walk but with a new laptop it changes the whole story hehe
If I decide to build a computer it will be because I want more experience with hardware. I might go for the GTS 250. Thanks guys!