If your current graphics card is connected through PCI express
, there is nothing stopping you from connecting a better graphics card, although you need a more powerful PSU
. Getting a PSU at 650W is definitely enough, unless you decide to connect 2 heavy graphic cards by SLI or use an crossfire solution.
Your CPU will be a huge bottle neck if you go for a new graphic card such as those you noted down.
So a short answer: get a new PSU or do as the above poster wrote: get a whole new computer system instead.