What is your PSU? the six pin is for the big cards that won't fit I believe they are from 8 to 9". Depending what size your PSU is then you can figure out the what card to get. I prefer Nvidia cards but the AMD/ATI cards are more bang for the dollar in lower end cards. If your PSU is 300w then the biggest Nvidia card would be GT 440. It is inportant to know the size of your PSU. Most cards can be found on newegg.com, amazon.com, tigerdirect.com ETC. Or go to the manufacturers web site of the card and check out the specs and requirements. I hope this helps a little.