Is this a decent gaming rig for a budget?

If you're going with a western digital definitly go with caviar black 32mb cache. This should be the minimum hard drive for gaming. I would also recommend at least another 2 gb of ram if not 4. If the motherboard has 6 slots you're going to want to load them evenly for max performance. So if it has 6 ram slots fill up 3 or all 6 if it only has 4 fill up 2 or all 4. Dont load them unevenly it will effect performance. so if it has 6 slots and you only load 2 or 1 it would really bottleneck performance. Look at corsair for power supply look for at least 650w. since you went with amd go with radeon. I tried to give you budget minded advice good luck