I am considering upgrading my Sapphire ATI 4830 graphics card to a 5770. I am wondering how much of a performance gain I can expect or if it is even worth it. I do some fairly heavy gaming but not super high resolution (1440x900). My 4830 has served me well and it still seems to hold its own against newer games, but if I will see a large improvement with the 5770, I'll pick one up. Thanks!