TBH, I don't think that's a great strategy, but I suppose it's what you want to do. I would rather purchase something much cheaper with a much better price to performance ratio, and upgrade it bit by bit as the years go by. But then I'm more of a "wheeler dealer", I like to buy and sell parts so I can upgrade with only a small loss.
The 950 is most definitely not
worth twice the price of the 920. You can simply overclock the 920 and it will sail past the 950 and even the 965. However, since you're going with the 950, I take it you don't overclock, in which case, I see no reason for a $300 motherboard, the MSI I linked to in my previous post would be fine.
And that GTS 250 isn't a great deal, this
most certainly is, and it would walk all over the 250 if you decide to get back into gaming again.
EDIT: And you want SATA disk drives, not IDE. Why two BTW?