Cf r9 270 or Cf r9 280x help

[Vdries]

If you had a chance of cf one of these cards wich would it be? The only downside is if I cf my r9 280x I need a new psu with more pci-e connectors.

And If you would cf the r9 280x, how many watts do I need?

The cpu is a i5 4690

Thanks in advance
And sorry for my bad English.

 

[Suztera]

I wouldn't crossfire either really, I would push to a higher end single gpu.
You would want a decent 750W psu for a R9 280X.