Price-wise be sure to compare final configurations again the Core i7 & i5 CPUs.  In some cases stepping up from the Core 2 Quad may not cost much and may be a significant boost in video editing.
Skip RAID get a big NAS (2x or 4x the size of the computer storage) and Acronis TrueImage software for backups.
(RAID is not a backup scheme)
HP, Dell and the the others are just re-badging OEM junk in a lot of cases these days - it's hard to say who makes it any more.  My last Dell notebook and desktop weren't made by Dell...
Yes, been looking at the i& stuff just a bit earlier.  Basically it means going to a Workstation config.  I have had good luck with RAID 1.  I backup offsite and on local HDDs.  Still, twice now having RAID 1 allowed me to continue work uninterrupted that would otherwise been a disaster.  Going to a NAS is a bigger investment and management issues I don't feel like dealing with.  If Drobo didn't have such bad QC and horrible CS, I'd jump on that.  Unfortunately, reality isn't meeting up with theory there.