That's a CYA because they understand that the market is flooded with poor quality PSUs that can't deliver their rated powers. Take a look at this sytem with a highly OCd, power hungry i7 965 and a MSI stock OCd HD7850: http://www.guru3d.com/article/msi-radeon-hd-7850-power-... The system only consumed 254W at full load. Your i3 2120 and stock-clocked 7850 will consume less; probably under 200W at full load. The CX430 is more than sufficient for your PC and OC for your 7850.