with gpu and not sound cards...sound cards are for audio on a pc not your video card. with gpu you look at there model number to see how old the card is. ie 3770 is older then the 4770. your 5770 was replaced with the 6770 and newer 7770.
with each new model the gpu core chip gets tweaks and more powerful. the newer 7770 cards use less power then a lot of the older gpu of the same model.
http://www.amd.com/en-us/products/graphics/desktop/6000...
http://www.amd.com/en-us/products/graphics/desktop/7000...
also the newer cards can do the newer version of microsoft direct x.
also the core tech in each card changes from one rev to the next.