I like Penguins, just not on my power supply :-P
A 500W (with 2-18A rails) give you some nice room to play. Honestly for $130 don't waste you money on the lower end cards, get an entry level gamer card like the 5750. It will give you MUCH better performance than a 4670 or GT240. It will run perfectly fine on that PSU and will run any game at your native 1280x1024.http://www.newegg.com/Product/Product.aspx?Item=N82E16814102859&cm_re=5750-_-14-102-859-_-Product
PS. You take the total 12V wattage rating. Lets say it is 300W. You divide that by 12 volts to get 25A. So 300W/12V =25A. Just a nugget of info since you said something about it.