Fair enough on the future proofing thing.

But DDR3 is out so all DDR2 motherboards will be useless eventually lol.

It isn't so much how much memory you have (up to a point that is: between 4GB and 8GB doesnt really make a HUGE amount of difference) but at how fast it runs. It would be better if you had a fast set of 4GB with very tight latency timings rather than a slack 8GB set.

Adn for all the video editing and autocad, its probably better to have a solid fast processor with a big cache as well as decent RAM