I'd like to qualify my information before it's too late:
With one 7850 under full load in their system, their PSU pulled 256W from the wall outlet. Their CPU was idling, so I have to add 77W for the i5-3330. Adding 77W makes the PSU pulling 333W from the wall outlet. So if the PSU is 85% efficient while pulling 333W from the wall outlet, then that means the system is only pulling 283W from the PSU. Your actual gaming load will be closer to about 225-250W.
The only reason I recommended a quality-made 400W PSU is due to what's commonly available on the market. In other words, it's going to be significantly easier to get a quality-made 400W power supply for your system than a 300-350W unit.