Welcome to the SeeMeCNC Community

I bought this power supply http://www.amazon.com/Regulated-Switchi ... wer+supply
When I first tried it would heat the bed two 90 c in 20 mins. That was at 12.2v there is an adjustment so I cranked it all the way up.
Now I'm getting 15.6 volts and the bed gets 90c in 9 mins. Im using two 14 gage wire for both power and ground. Im happy with it.

It will be interesting to see how long that power supply lasts. Running it at a higher voltage.

The adjustment knob on those are for fine tuning the supply to the rated 12v. (13.5v-13.8v)

I use these a lot in my projects but never really over volt them intentionally.

Not all of these are great though I've had a couple faulty right out of the box. Thats china quality control for ya.