Discoloration of the motherboard near the powerside and the same issues with capacitors you already discovered on the graphics card are pretty good indications of a problem. You will want to remove the motherboard and check the bottom side too especially around the area that the AGP slot is and around the psu plug. Visual inspections are okay but not always revealing but if you see something obviously wrong...
...Based on the CPU a lesser card might equal equal performance...$65 http://www.newegg.com/Product/Product.aspx?Item=N82E16814102814