When your website is growing and this growing traffic and storage demands a high security, then I suggest you to choose dedicated server. Dedicated server includes the highest amount of RAM, Bandwidth and saves website from virus attacks. You can delete the negative effect of performance of website due to poor load time by using dedicated server.
You have to log in to your server's WHM panel as root and go to Manage root's SSH Keys in the Security section. Click the Import Key button. Type a name and a passphrase for the key. Paste your public key in the corresponding field.