I am now thinking about getting this Power Supply, its an Antec Earthwatts 430 Watt EA-430D GREEN
Good Choice and yes it would "work" with the 6670. Most Power supplies and cards are compatible if it had adequate wattage.http://www.newegg.com/Product/Product.aspx?Item=N82E16814102952
I don't know. This was the power supply I was looking at http://www.power-on.com/ea460u.html
On the site it said it has a 20pin+4 so yes it is a 24 pin PSU.
its separate because some motherboards only have 20 pins.