Im probably going to go with the 6870. To assure it works i want to go over some things. I have a pci express 1.1 slot but the card is backwards compatible. I have a 650 watt psu. I have 2 6 pin connectors. I also am assuming that my mobo can take 1gb of ddr5 instead of 1gb ddr3. It is also a big card about 10 inches long correct? Also, is it safe to use catalyst control center auto tune feature or would it be better if I just overclocked manually if I did. Is it safe to have a gpu fan at 100% all the time other than shortening its life?