Depends on your budget. But before buying a whole new computer, I'd look into upgrading. Your CPU isn't the newest, but it's not too weak for the game, and you have plenty of memory... it's mainly the video card that needs more power.

Useful lower midrange cards include the Geforce GTX 650 Ti "Boost Edition" (long name, but Nvidia sells several other, weaker 650 models) and GTX 660, or the Radeon 7790 and 7850. In all cases, aim to get 2 GB of video memory. 1 GB is too little, but more than 2 is unnecessary unless you game at 2560x1440 or above.

For comparison, my old video card (that will be upgraded probably when the next generation of Radeons hits at the end of the year) is comparable in performance to a 650 "Boost Edition", albeit with only 1 GB VRAM. I have all settings maxed out at 1920x1200, and depending on the situation I am getting between 30 and 40 FPS, without any significant drops. That isn't overly much, but it's smoothly playable at the full beauty this game can offer. Score in the character creator benchmark was around 5400.