Check out the new image backup software, they can even do reliable image backups of RAID while the server is still running these days. I've tried Symantec LiveState, UltraBack, and Acronis True Image, which is what I use on my most critical systems. A little more bleeding edge is the "universal restore" feature of these products, where you can restore to dissimilar hardware. That only seems to work about half the time, but when it matures it will be holy grail of restores. But of course, nothing beats having a perfectly matching piece of hardware sitting there ready to go if and when the need arrises. Just make sure you order them at the same time, because even though model numbers stay the same, internal components do not!
The main things about restoring a RAID array seems to be the CPU and chipset, the RAID controller and the drives themselves. Adaptec controllers seem to be available forever. I have a half dozen spare drives, all purchased at the same time. Windows says the only critical thing is the controller. We shall see.