PSUs that come with the case and therefore are generic is a NO-NO for a PC like that.
Also, speaking about power issues many people often overlook the need to buy adequate power protection when putting together or buying their PCs. Power surges can damage parts instantly or degrade them overtime.
People who have unexplainable restarts, reboots, or general weird problems that cannot be isolated to an internal PC component might just be victims of power spikes and surges.