As long as you are buying it from Macsales, and it has a lifetime warranty, it's all good. My desktop has OWC RAM in it and it works great, and I'll be getting some for my laptop. One of the sticks in my desktop did go bad and when I figured out it was the RAM and called them, they made arrangements for me to ship it back and get a new one coming right away.
As for firewire (not firewall) hard drives,
Macsales has them too.