Since the HDD is likely to be the bottleneck, I'd look at this thing... Amazon link follows.
http://www.amazon.com/Corsair-Accelerator-Series-Cache-CSSD-C60GB/dp/B007HBLFWW/
I doubt more RAM will give as big a boost as a faster HDD system.
About the 100% RAM usage. You do realize this will remain 100% even if you max this out?
Bob
I have a 2010 dell xps 8100 with these specifications:
i7 860- fine
1gb ATI graphics card- good enough but maybe an nvidia would be good since After Effects supports offloading rendering to nvidia but not ATI (right now it is CPU rendering which is slower)
6gb ddr3 ram- definitely nead 12 or 16gb
usb2- I will be upgrading (if I choose to upgrade rather than start from scratch) to a couple usb3 ports along with a 3tb usb3 hdd
standard 7.1 realtek hd surround sound- fine because I don't do that much sound design or editing
not sure about power supply
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So... AE/PP (after effects/premiere pro) uses just about 100% of my RAM- really bad. This is the main issue I have. I don't plan on getting new software anytime in the remotely possible life of this computer, so that is not an issue. I am MOSTLY fine with the computer except the RAM. A new video card would be nice, but I can live without. I make little vids just as a hobby in high school, so time does not equal money for me. I don't have to worry about deadlines or other professional hazzards. It just gets bogged down with all the layers of footage to composite.

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