Minimum Power Required For PSU??

[meateater]

I am going to build a computer with a R9 270 and the specifications say it requires 500W Power Supply needed. I just saw in the "System Builder Marathon Q3 2014: Budget Gaming PC" that they used the exact same R9 270 with a power supply lower than 500W.

I'm a bit confused as I am a new builder. Help would be appreciated before I finalize my list.

 

[Suztera]

A decent 450W power supply will be fine with a R9 270 build but getting a 550W or 650W will cover any single gpu upgrade you make in the future.
The specs requirement 500W to cover the lower quality power supplies that says they are 500W but doesn't actually provide 500W ish on the 12V rails.

Anything from Tier 1 and 2 from this list is fine to use:
http://www.tomshardware.co.uk/answers/id-1804779/power-supply-unit-tier-list.html

 

[Dark Lord of Tech]

A Radeon R9-270 needs 24 amps on the 12v+ rail and a 500 watt power supply and 1 6 - pin PCIE connection.

A solid 500w - 550w would be a great choice.

PCPartPicker part list / Price breakdown by merchant

Power Supply: XFX 550W 80+ Bronze Certified ATX Power Supply ($54.99 @ NCIX)
Total: $54.99
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2014-10-04 16:45 EDT-0400