most cheap hunks of junk can run just fine on a basic OEM PSU...but the reallyyy good shit needs some extra power

You'd need to specify what model of Radeon graphics it is. Radeon is just a brand, it doesn't mean anything. It's like saying you have an HP computer. From there, we can determine if 220 watts is enough to power it (it's 99% likely it won't be). I can definitely tell you that even if you got an awesome graphics card, your CPU is going to bottleneck your performance. A Pentium is a business class processor, it's not designed for gaming.