Is HD4200 good for 1024x768 and lower gaming?

Hello, so I have an HD4200 IGP that I use on my computer mainly for office productivity and hd video watching/the occasional non-HD video converting. However, I also sometimes (very infrequently) play moderately-intensive (eg. DIRT3, Skryim) games at 1024x768 or lower (800x600 for many of the more graphically-intense games). So, I was wondering whether an HD4200 would suffice, or if an upgrade is required. Since I have a 250Watt power supply, AMD Athlon ii x4 645, and 6GB Memory, I don't think my PSU can handle anything above an HD5450. With this in mind, do you suggest that I put in an HD5450 for just stay at the HD4200 (since it would generate less heat, quieter). Bear in mind that I only play games very seldomly, and they are mainly RPGs, and so are not graphically-intensive like FPSs. Thanks!