If you want a serious answer, then I don't agree with you - and I don't think RAID is a particularly cost effective (or good) solution for home use. To do RAID properly you should have at least two identical boxes (since you're introducing an extra point of failure in the box/controller itself) and then have some backup strategy. I think backups are also more difficult to organise if you have a large amount of contiguous disk space compared with separate drives, which can be quickly duped onto another of the same size.
2 boxes for RAID ? Do you know what RAID is ? I'm not talking enterprise grade clustering with hot failover here, just a simple "drive A fails, Data stays online" type setup. RAID-1 or RAID-6 is plenty good for home use depending on the size of the array and number of drives. Heck, some newer boxes can even do parity based arrays over different size disks. No more worrying about having identical drive geometry.
The point is, boxes rarely fail. Drives are the most unreliable components you have. Make those redundant is the best way to assure your data is kept online. Boxes and controllers are quick fixes if they do fry, so are power supplies and none of those can really cause data loss. A failed drive that isn't properly mirrored or in a parity setup will take your data with it to the grave, forcing you to recover from a backup.
Additionally, in my experience RAID boxes for less than £500 generally have cheezy PSUs, underpowered CPU and nasty small fans. £1000 for two of these even before you start adding disks or thinking about backup is money poorly spent. RAID is also at its best when used as a solution to maximise uptime - not a data integrity solution (where I don't believe it's cost effective in a home context).
Which RAID boxes do you own? How many of them?
I own a QNAP personally. I looked at the "build your own" solutions, and seriously, for the price, way too much of a hassle. 500 mhz CPU (which is faster than what is in the FreeBSD box...) is plenty fast to drive a gigabit network link and a RAID-1 mirror.
The thing about computing power in the last 10 years... it got infinately useless for most tasks. CPUs sit idle most of the time doing tasks you'd think were intensive (and probably were... 15 years ago). A home NAS doesn't require teraflops.
As for "cheezy PSUs", I haven't had a PSU fry a drive in over 20 years because of voltage spikes or other crap. Buy snake oil all you want, the PSUs in the NAS boxes are fine.
Housing disks in a Mac Pro means you have them in an excellent PSU and temperature controlled environment which runs quiet, and has very fast access. I run multiple 2 and 2.5TB disks JBOD - and use a 2 bay WeibeTech caddyless hot-swap enclosure to enable a rotating backup strategy onto same-sized disks (including offsite). I'd rather spend my money on more and better backups than some slow RAID enclosures.
As I said, RAID + backups. RAID is not a backup solution, it's meant to keep your data online in the case of a failure. Restoring from backup can be time consuming and losing just 1 drive in a RAID-0 or JBOD can mean serious downtime and recovery, especially with "offsite" backups. And not to mention RAID-1 with hot swap drives is probably the easiest thing to backup. Just pull one drive out and put in a new one. Instant backup (though I don't recommend HD based backups, for home use, tape is too expensive).
As for housing them in a Mac Pro, again, fine if that's your only computer. Welcome to 2010. Well, at least, when you move out of your 1 bedroom appartment and start living with people instead of alone.
I also don't have a team on my network. Just me.
That'll change once you get a GF and some kids.
EDIT: Forgot to mention a NAS box will draw much less power than your Mac Pro, which you could then shut off to preserve electricity and keep your monthly bill a tad lower. I'm actually tempted to get rid of the PC running FreeBSD and get a Mac Mini instead just for the power factor alone, since I don't even need the RAM/power upgrade it would provide.