That would be fine for a while. But to be really future-proof go for 480 or 550 watt. Antec's TruePower line is highly recommended. I have the Antec TP 550 watt PSU myself, and it's really excellent, silent too!
My system: AMD Athlon XP 3000+ CPU / TwinMOS 1Gb DDR400 / Soltek 75FRN-RL /
Sapphire Radeon 9800 Pro / Antec True Power 550W / Maxtor 80Gb ATA-133 / Hercules GTXP SC /
Samsung DVD / Lite-On CDRW