I'm keenly aware of the double expense. I look at it in two ways. One is by taking the total cost when considering overall value, as you suggested. The other is in terms of the overall build in relation to my original budget. I'm currently around $950. So adding in another $300 would still put me ~$250 under budget; plenty of room for a proc upgrade. Also, I'd probably try to sell the old proc and GPU, so at least some of that money would be coming back in.
As far as integrated graphics are concerned, I had spec'd a 6770 a while back, but was told that it probably wouldn't have enough oomph to get me by. Would I really be able to game without a dedicated graphics card? (that's not rhetorical.) Don't get me wrong, I wouldn't mind going straight to the next gen, but with no firm release date, it seems like an interim solution is sufficiently warranted.