The PSU may or may not be up to the task (IMHO it's probably up to the task, but just barely, so any loss of efficiency and he's sunk), but I'm wondering if maybe the PSU wasnt' damaged from excessive heat. According to the parts list there's only one case fan. I can't see how you could cool that computer with only one fan. One of my boxes is a lot less powerful and still has 4 case fans. The daily driver (i.e. the powerful one) has 4 as well, and if they weren't 120mm (with one 9cm one on the side) I'd need more than that.
If I were you I'd add a case fan or two, and replace the PSU with something that'll be a bit more comfortable. I like Sparkle and Thermaltake Toughpower PSU's. Get a 600 this time
