Get a nice 500-550 Watts power supply, Enermax or Antec. That way for a long long time you don't have to bother about having enough juice or not. The cost isn't high if you think about the years of trouble free use you will get out of it.
Anyway, I think the 9700PRO will not like to share that 350 Watts (maximum) with the rest of your toys in that case.
<font color=red>Got a silent setup, now I can hear myself thinking.... great silence</font color=red>