Since you are using 10GB disk space now, I would suggest you:
1. Share a server with another person
2. Get yourself a dedicated server
From what I know, a 10GB diskspace VPS + WHM/cPanel is really costy and it is only a little bit cheaper than a dedicated server.
If I were you, I will look go for a P4 server. Nowadays, you can get good P4 servers easily between US$100-200/month. You can try managing the server on your own since you have cPanel on the server. Do some research in cPanel and I'm sure you will be able to catch up fast.
Hope that helps.