HD 6950 should be the same cost as 560 TI and should perform better.
Even if the Thermaltake PSU is a gift, I would think HARD about subjecting $800 worth of my computer parts to it. This PSU is worth the price you paid for it ($0).
Much money is being wasted on having a motherboard that is not appropriate for budget builds. A good micro board will do everything the chosen board will do for half the price.
You could use the difference to move up to a Thuban x6 1100T
you could use the difference to get a good PSU instead.
- edit -
i mean most parts in general.
it will probably be around holiday 2012 before i finish it.
If you are seriously considering buying something now with the $300 from this Christmas and then just leaving it in a box until NEXT Christmas, DON'T. Save the money until next Christmas and then make a full build instead. There is no good reason to spend any money now to buy something when the same money a year from now will buy something 20% better.