I concur with Jonathan on this one. Reseller definitely seems the way to go - not only does it give all your users their own cPanel it also helps you monitor and maintain each
website hosting individually and monitor things like how much bandwidth a certain
website hosting is using.
Unfortunately if the server goes down, the server goes down. As Jonathan said you can split between 2 servers but you will have to think of the financial implications of this and if it is really worth it to yourself. I can't imagine that theres been too much downtime of your server has there?
