Move your Project files from D to E, and use F for exports.
Please someone correct me if I am wrong, but I think you would bennefit more from a faster processor, i7 3930K, instead of faster disc system. The DSLR footage does, as far as I know, not take that much bandwith inside the system, but is more compressed, and need a quite fast processor to decode.
Maybe an Nvidia 570 would be a good investment to.
I would disagree with that suggestion for the simple reason it would require a new motherboard and possibly new memory as well. The i7-3770 is not bad at all, apart from the default cooling paste.
If the OP wants to improve performance on the cheap, I would suggest a second 500 GB disk and then configure them in a raid0 for media cache, pagefile and previews.
Thanks for clarifying it Harm, I assumed the MB could be used for the 3930 CPU, but obviously not. :)
As was said above the faster the processor the higher the performance, unfortunately it appears that you have a locked processor. If it were an unlocked processor like the i7-3770K, you could easily overclock it and gain significant speed.
Also depending on how many MPE assisted effects and features that you use going to a newer nVidia card might greatly assist in your output encoding. My favorite sweet spot is the GTX 660 right now, much more performance thar your GTX 285 and less power/heat.
Plus follow Harm's suggestion of a RAID 0 array