1) It's hitting 5 years old pretty soon and it was only of decent quality. So that Enermax would not be a good idea to use.
2) No. It's missing that extra 4Pin for the main motherboard connector
The Corsair 400CX 400W PSU is one of the best PSUs for $50. However, whether or not it has enough power for your planned setup depends on which AMD AM3 CPU you're planning to get. "AM3+ processor/motherboard" doesn't help us at all since AMD CPUs vary in power usage from as low as 45W to as high as 125W. So please tell us WHICH AMD CPU you're planning on buying.