New machine specs?

Hi all,

I need to build a new acad computer to replace the aging P4 which means I have several questions:

1. how many cores/threads does the current acad support?

1. of the following, which is more important? cpu speed number of cores/threads amount of ram speed of video card speed of hard drive subsystem

2. Is there a big difference among scsi, ide or sata?

1. Does raid make sence for acad?

thanks for any feedback, charles.....