^ what are you talking about?
to OP. your computer, for the most part is good for what your doing with it (editing). as far as I can see, these are the components id change, starting with (in my opinion) most needed to less needed:
Nvidia GPU (gts 250, gts 450 or 460, or gtx 650, all with 2 gigs of memory if possible, although not an absolute need. depends on how much effects and ect your adding into the project. anything higher than these cards, and you really wont see a difference in performance with editing.)
650watt to 700 watt power supply (seasonic, corsair, ect...)
ssd to load windows and your editing software, and using your raid 0 drives as your scratch disc and destination (working) folder.
as far as your cpu, it is a good cpu for the task, but could be improved if you could raise the speed of it. lastly, id recommend getting a motherboard of the same socket and chipset (1366, x58), so you can overclock it to 3Ghz, or more. grab a aftermarket cooler as well so you keep temps where they need to be. this last upgrade will tie it all together nicely, but is sort of pointless if you don't get the 1st 2 upgrades first.
and getting an i5 over an i7, regaurdless of socket, is ignorant in my opinion considering your doing editing. for gaming maybe, but having 8 threads over 4 makes a big difference in editing. I do a lot of editing as well, and have learned that the upgrade path I showed you is for sure the route that will fit your needs best.
everything else you have will be fine to use. even if you get another motherboard for your 920, the dell case will still be fine. you may have to do a little change up with the fp header, but let us know and we can help you out with that, so no biggy or concern. the ram you have is fine too, although I am wondering how many sticks of ram are installed, and what is their speed? be sure to run 3, or 6 sticks of ram, so you get tri channel mode on your ram. if there is 4, or 5 sticks installed then remove some so you have 3, or 6, otherwise it will drop the ram down to dual channel mode.