I wouldnt call it a "hard-core" card, it is good though. BTW Trix I sent you a PM regarding your question. The way it is possible to have less power drain sometimes is if the x300 is seriously taxed by something it will more than likely use more power than the 6800 because it only has to work half as hard. I do think the battery life would be better on an x300, but not enough so that I would sacrafice the performance. Besides you are going to have 1GB of ram, what do you need that for? Certainly not for a game, because you are gonna max out that video card long before it maxes the ram. You doing rendering? Video card would help out a ton there. I think the same for photo editing. Any intesive application that will use 1GB of ram, would almost assuredly benifit from the extra video card oomph. Plus you gotta wonder what it will do to resale value.
If you are gonna skimp on the video card, I think 512MB of ram is another good way to save money. As it is your lappy has unbalanced power.