Should I buy new or use this one? I don't have much cash so I don't want to change it unless I have to.
More aboutbuying system change
PSU should be fine. Go with the 4770, more powerful card but uses less power.
Can I ask why you adviced 4470 instead of a 9800gt? Because I was thinking I would go for the nvidia. I used a 6800gt for 4 years and I was quite content with it. Besides I have to get something which has linux driver support which I belive ATI has/had issues with it. But on the other hand I've checked a few benchmarks about 4470 and it seems it has better performance than 9800gt. Was that the main reason you've adviced me or was it just about the power it uses?