Required wattage GA-8IPE1000G

Guys, I'm considering buying the GA-8IPE1000G motherboard for my HTPC
system. Right now I've tried using an Asus P4S533 but apparantly due to
the Sis chipset this mobo isn't quite up to specs. However the
limitations are a bit strict. The system only has a 320W PSU at its
disposal. Now there's nowhere in the manual that specifies the
recommended PSU power. I'm considering setting up the following system:

GA-8IPE1000G mainboard
NVidia 6600LE
Maxtor 80GB 7200rpm/udma6
1GB mem (2 512MB banks)
DVD reader
Soundblaster Audigy

With the P4S533 a 300W PSU is sufficient (the current case only provides
for a 300W PSU, the new case [HTPC version] does have a 320W mATX PSU).
Is a 320W PSU sufficient for the given setup?

Thanks in advance!
Regards,
Richard