Keep the Raid drive for your video. Install Premiere on the miscellaneous drive.

If you're editing DV-codec AVI video (DV-25 standard, as you would get from miniDV), you do not need 7200 rpm drives.

I don't recommend using a computer graphics card for editing. The gamma of a computer monitor is very different from NTSC/PAL television and it's nearly impossible to do accurate correction using one. Instead, get an inexpensive miniDV camcorder with AV passthrough. Connect it to your computer via 1394/Firewire and use the video outs to connect to a good-quality television monitor. Premiere is capable of real-time output via 1394 and, this way, what you see on the television monitor is what you get.

I actually use two television monitors connected in this fashion. One is a small broadcast-quality television monitor, the other is just a decent-quality television. This way, I get a very accurate image on the broadcast monitor, but can also see if anything is lost when the project shows up on a traditional television.