I've been evaluating the 1999$ model and the 2499$ model, and besides the HD size and CPU clock speed, the most significant difference is the video card has double the VRAM. I'd like someone more educated than me to help me understand if this is a significant improvement. Is the clock speed any different? Will I get more fps in gaming? Will 128mb of VRAM hold me back in gaming? Will it affect Vista performance? Essentially, what will the extra expense gain me? My gratitude in advance.