Power supply affecting performance?

I was hoping someone could settle an argument between me and a coworker.We have just built a machine for in office fun out of spare parts.Anmyway to make a long story short this machine is a 1.7 gig pentium, with 640 megs ram gforce2 64 meg video,52x cdrom, burner,and several usb devices.Also we added some fans and some col cathode lights.My coworker decided to install a 150w powersupply and i thought he should use at least 250.Anyway the machine seams to work as intended but my question is will the lack of available power affect the machines performance?