Backup Storage Options for storage RAID Arrays that are More Tolerant To Hardware Failures?

I'm looking at different options for getting a NAS/RAID array system that is tolerant to not just hard drive failures but also to hardware/firmware and board failures. I've utilized a RAID array in the past that was built into the motherboard, which resulted in the motherboard failing and me having to ebay another one to get the RAID array back up and running. Then I bought a NAS 2 bay drive that was only compatible with drives up to 1.5TB. I've also used external drives for backup since I've been burned by hardware/firmware/software issues related to RAID arrays. Are there are any PCI RAID cards, NAS boxes or software RAID or other options where the hard drives would still be readable by other RAID cards if the boards failed? Maybe a software RAID solution? Any thoughts would be appreciated.