My tower and two monitors are plugged into a power meter and while stressing the cores with Prime95 the power consumption is 310W. Add 50W max for the GPU and that'll total 360W. That's with 5 case fans and 5 hard drives too.
I think it's more important to go with a quality PSU; Corsair/Seasonic/Enermax
I use a 650 watt PSU here at work and my system has an Intel i7 920, Asus P9T mobo, 6GB RAM, GeForce 9500 GT, 16x DVDRW, 40GB SSD and a 750GB HDD. It's also a Corsair. Definitely adequate.
Like the others have said, it's much more important to have a quality PSU, not just a higher number on the label. You should be fine with that PSU. I've got a 550 watt running the rig in my sig, so you shouldn't have a problem.