Wattage for crossfire r9 270

[Joda56]

I have a msi r9 270 (not x) and wanted a r9 28-x but is a bit out of my price range. Now I'm thinking about crossfire r9 270.

And I have a few questions about this, one being what would be a good (cheap) psu that will work good enough?

My second is will a tr2 600w psu work? I know its a bad power supply but I didn't when i bought it.

My third and final question is what all problems could I have with crossfire?

 

[Joda56]

For some reason when i try to update thread it says invalid, but I am thinking of either Rosewill capstone 650w or a Zalman zm-650-XG