theres no problem with the card you have, ( check Caligari's list of recommended hardware click here ) . If you want faster performance get a faster cpu because this type of rendering demands more from the processcor and utilizes the graphics card less than a new game.
realistically short of moving to a silicin graphics workstation your machine is pretty much as good as you would expect . It may help to make sure that everything that you can possibly switch off is switched off while you work but real time rendering is a slow process so patience is the most important thing. PS a 10000rpm SATA hard-drive will help as well.