Actually, Intel chipsets come with Matrix RAID incorporated to the mainboard. Of course this will have an added cost, but those costs are normally well hidden among the plethora of components, half of which you may never use (e.g. Dual Gigabit LAN, 6x SATA come to mind).

Plus, with the Intel chipset you get the works - there are no "non-Matrix RAID" chipsets.

The reason for running backup software and still keeping RAID-1 is the following:

Once you install the operating system and the programs you are going to use, your system pretty much stays the same in terms of configuration. Therefore, running a backup for your OS and programs normally is a one-time deal.

With your work files, however, this is something you don't want to lose. If you play dangerously with RAID-0 and store your work files there, you either need to run backups daily, or risk losing a week's or a month's work (depending on how frequently you backup). This does take time - about 2-4 hours, depending on how many files you have. Even with incremental backups this can take an hour or two. Therefore, if you are prudent, you would backup daily with RAID-0, but that in turn takes a good chunk of time, which could be better spent on productivity or gaming.

Plus, with RAID-1 you don't need to restore anything - you still have one operational hard disk to grab your data from. 

Without question, the video card is the number one most replaced part in my pc. I probably replace it with a mid-range card ($200) every other year. As I stated earlier, this is a problem right now as there aren't any good values at that price point. Oh, and get the biggest, baddest PSU you can afford. Note that doesn't just mean wattage, it means get one that's stable and reliable. I have an Antec trio 660, it's a rock and will probably last me through several iterations of upgrades. The only reason I got it to replace my old Antec (which is still running in my htpc), though was because of the new ATX specifications.

If you're dead set on getting an AMD chip, I urge you to wait until their new chips arrive. Otherwise you're throwing away performance. Simply, the architecture is at it's life's end and can't compete in any way except for price point. It's funny, because just a short time ago, the exact opposite was true, AMD had the cutting edge architecture and Intel was trying to squeeze performance out of the dying platform (P4). Heck, if you wait a few months, I bet there'll be some nice video cards out there that will actually perform well for around $200.

For me, hard drive speed is more important than hard drive space.  If you bought a WD Caviar 750GB, you'd be spending more $/GB, but your computer would feel much faster.  Your hard drive is the slowest part of your computer, therefore it has the most noticeable impact on performance in day to day tasks.  You don't sit around waiting for an application or game level to load because your CPU isn't fast enough or your video card isn't DX10-capable.  You sit around waiting on your hard drive to load the data.  Believe me, a fast hard drive can make all the difference.

And the Raptors aren't worth it anymore, their speed is outclassed by the fastest 7200 rpm SATA drives now.

I still favor space, but speed is very important, hence my using Raid-0.

I've got two Caviars (250GB each) hooked up to my gaming rig, and with Raid-0 you can definitely feel the difference.

Raptors were never worth it in my opinion, but those new solid-state drives are looking interesting. Still too expensive IMO, but its time will come soon enough. 

 I think that needs at least a year more before it hits the affordable range.

 I agree with the rest of your post, but this?  Source plz.