Depends on your other hardware. I had an AXP 1600 OCed to 1600Mhz running on a 235 Watt
PSU but that machine only had the basics. ATI Rage video card and NIC were all it had. It used the onboard sound and had a 5400 RPM HD. It ran fine like that. Eventually stuck on a better video card, DVD player and CD burner and upgraded to a 350 Watt
PSU. I didn't try it, but I don't think that setup would have worked with the 235 Watt
PSU.