As long as it's an older style unit with hefty 5V and 3.3V rails, then yeah, it'll be plenty. A 250W PSU was on the high end in the PIII days... PC hardware didn't use very much power back then.

For awhile I run a P-3 866 with Voodoo 3 3000 PCI and Geforce 4 Ti4200 in it with only 150W PSU - MicroATX case with SB 5.1, 2x256mb ram, 320GB 7200 HDD, DVD-RW. There where problems with graphics drivers so now I only have Voodoo 3 AGP in it and it uses maximum 60W on the outlet.

This system ...

PIII Tualatin 1400S @ 1.6
440BX
3x 256MB RAM
Geforce 6200
AWE64 Gold
1x Promise Controller
1x SSD
1x HDD
1x DVD
1x Floppy

... draws 90W from the wall on full burner, and that with an ancient topology low efficiency (80% or less) PSU. 90 x 0.8 = 72W .

I'd be very surprised if your system ever draws 150W. A Kill-a-Watt gadget can be very enlightening on these respects.

looks like it will be fine, thanks for the answers.

though the driver issue kixs mentioned is interesting, Ive heard of numerous examples of a Voodoo3 working with a Geforce card just fine.

could be an issue with the GF4? or potentially the particular version of the Nvidia driver, I tried fairly late drivers on my GF2 Ti and it gave me various issues like all the textures disappearing in No One Lives Forever, or Unreal not working in D3D mode, reverting to the older 56.64 drivers fixed all those issues, so it may very well be something of that nature.