Hi,
I have an old Sony Vaio PCV RS431x computer that had a 300w psu in it. A couple years ago, I thought the PSU was going bad and bought a new one here:
http://www.atxpowersupplies.com/400-watt-Sony-MJPC-300A2-power-supply-LPM2-20-P4-M.php
I think the one I bought might be 300W or 350W...