or create a symbolic link from the default data directory to the other hard drive.
Oh, awesome, so it's pretty easy then. That's good to know.
IIRC Armory and QT use the same blockchain data.
Not anymore, since 0.8.7 Armory has had the Blockchain totally separate. I believe Armory still requires an install of bitcoin-qt be running, but it has it's own version of the blockchain now. It's a bit out of date on my computer because I haven't run Armory in a few weeks, but there's definitely a copy of an (old version) of the blockchain. It's in C:\Users\[UserName]\AppData\Roaming\Armory\databases if you're using Windows, essentially the same location that bitcoin-qt stores its blockchain. It's a tradeoff Armory makes between hard drive space and RAM, it used to require 6+ GB of RAM to use, now it just requires O(2N) of the blockchain to use, where N is the size of the blockchain.