You probably won't be able to run a 6670 on that PSU. 16A on the +12V gives you 192 Watts to work with. Keep in mind that +12V also powers hard drives, optical drives, and fans, as well as the CPU and GPU. Best case scenario, the card would run but you would be pushing your PSU to its absolute limit, which is not good for system stability, or the lifespan of the PSU. More likely, your computer will shutdown if you put a heavy load on the 6670. The most powerful card I would recommend for that PSU would be a Radeon HD 5570, or possibly 6570, everything above that draws too much power. If you do want a 6670, a 300 Watt PSU would be the minimum for that.