For speed, another top upgrade is to store “raw” video files on a second storage device, other than where the operating system and applications reside.
You might consider the simple option of an additional internal 7200 or 10K RPM HDD, or maybe something like an external, two disk RAID 0 attached via USB 3 (economy choice) or Thunderbolt 2 (faster & $$$).
I play with video projects that are small, esoteric, and usually shot at 720/24p. I’m using FCPX on my Mac Mini, 2.3 GHz quad i7, 16GB RAM, external USB 3 dual SSD RAID 0, 27″ Samsung HDMI 1080 TV/monitor. The system is adequate for me, but I have an extra 22″ LED monitor I’m not using, and I plan to bump up to dual monitors soon to see if extra screen space is a good upgrade for editing.
