Bear in mind that some games 'just do that sort of thing'. I cant speak for the games you are playing, but certainly Bioshock Infinite likes to lag out when running on my more than capable desktop. Deus Ex HR was the same until the devs released a fix in an update.
Don't disable V-sync. This just leads to ugly tearing in games (very obvious and annoying with ATI cards I find) and puts undue stress on your GPU for no good reason. What to do is get some monitoring software that allows you to display resource utilisation in top left of screen, then you will be able to see if something is maxing out during frame crashes.......if not, it is probs just a bug/driver issue.
Don't disable V-sync. This just leads to ugly tearing in games (very obvious and annoying with ATI cards I find) and puts undue stress on your GPU for no good reason. What to do is get some monitoring software that allows you to display resource utilisation in top left of screen, then you will be able to see if something is maxing out during frame crashes.......if not, it is probs just a bug/driver issue.