I wouldn't use a online wallet at all.
Personally I would install a linux distribution like Ubuntu (LTS) or Mint that lets you choose "Encrypt home folder" during installation.
Then I would install bitcoind and let it sync with the bitcoin network -
http://rdmsnippets.com/2013/03/12/installind-bitcoind-on-ubuntu-12-4-lts/Then install Armory and create a few accounts.
Then make a paper backup of each account . Optionally you can save those to pdf if you want to print them somewhere else, but remember to delete those pdfs after.
Then print the backups to paper and hide them somewhere safe.
Transfer your coins to the armory accounts.
You can delete the .wallet files of some or all of the accounts in the .armory folder if you don't want to have them around on your computer.
As long as you have the printed paper backups you can restore your accounts on any computer at any time.
You can even use them to restore your accounts on several computers if you so desire.
I'm sure there is other ways to go about it. This is just how I would do it.