For a system using a single Radeon HD 6670 graphics card AMD specifies a minimum of a 400 Watt or greater power supply. The power supply should also have a combined +12 Volt continuous current rating of 19 Amps or greater.
Total Power Supply Wattage is NOT the crucial factor in power supply selection!!! Total Combined Continuous Power/Current Available on the +12V Rail(s) rated @ 45-50°C ambient temperature, is the most important factor.
The Antec Basiq Series 350 Watt (BP350P), with its combined +12 Volt continuous current rating of 23 Amps, is sufficient to power your system configuration with a single Radeon HD 6670.