NVidia GeForce 8800GTX, not enough memory?

Hi Folks,
My PC is built on an Asus P5N32-E Sli Plus mother board, Intel quad Q6700 @ 2.66GHz processor and an NVidia Geforce 8800 GTX 768MB graphics card, running Win7.

Photography is my hobby and I have recently been adding some simple 3D text on top of a few photos. The problem I’m having is that Photoshop crashes if I try to go above three words of text.
It reports that there is not enough memory on the graphic card. As my mother board will take two graphic cards, I’m thinking of putting another of the same in.

So would the whole of the combined 1536MB of memory be available to Photoshop and cure the problem?

Any advice would be appreciated

Thank you for the fast response........... looks like I'll have to get a new graphic card/