The CPU is the retail version yet you are buying another HS fan? Why not get the CPU only? 4GB Ram? It wont all be seen by windows. 2GB is ample and get some low latency ones. No mention of a good PSU. I would be inclined to add another HDD. A WD 150GB (or 74GB) Raptor to run OS and games. Your WD Caviar (Hitachi Deskstar for Document storage and an image file for backup. A bigger monitor would also make an awful difference, something like a 22" one.
Performance versus cost means the Q6600 is still excellent value. However I would check what voltage you're advised to run it at to 'guarantee' 3.3GHz.
Most Q6600 on sale now seem to be the 95W G0 stepping model which is supposedly the best for overclocking although every processor requires different voltages.
I can guarantee mine to 3.6GHz but only if I up the voltage to over 1.6V. I can also guarantee mine to 3.3GHz (which is what it runs at) but with a voltage of 1.48V. Mine isn't the best example of an overclocking Q6600.
Increased voltage means increased heat and a good quality heatsink e.g. Thermalright Ultra (Extreme)/Noctua NH-U12 is needed. There's a slight to moderate chance that with an increased voltage that its life may be short.
The Zalman cooler is reported as good but noisy. Check out Frostytech for reviews particularly the temperature comparisons at the conclusion of the article click here