I think the Q6600 still is a very good CPU, mine outperforms almost all default clocked "modern" cpu's. It runs like charm on 3.6 GHZ or higher if i need it. Just be sure you get a SLACR and not a B3 stepping.
For video i still should go for NVIDIA, i have had bad experiences with ATI in combination with RACE. Enough FPS but stutters in the corners. I know many people have issues with NVIDIA too but after my switch i never had the stutters again and it performs very solid.
For video i should wait for the DX11 versions, they will be here very soon.
OCZ is good RAM, i use it too and it's kinda cheap these days.
I don't have experiences with DFI, but reading the reviews it must be a great board, my choice is still Gigabyte or ASUS, i use Gigabyte and this is the board i trust most of all boards i owned. They use very expensive voltage regulators, it looks like overkill but better have overkill than underkill (what word, underkill ).
Which powersupply you get? This is very important, take 600 real watts or more. Look for Corsair, they are amazing good.
Directx11 is coming out with Windows 7. Late 2009 if MS don't delay it (unlikely).
I had a gigabyte, they are ok, no way near as good as a DFI. Also they look like they have been coloured in by a 5 year old with a new colouring set :thumb: