i will suggest you the reseller hosting package of varyhost.com, they provide unlimited diskspace, bandwidth & unlimited accounts, free merchant account free whmcs and many other features im using this package hope it would also be gud for you Hope that helps
Shared hosting won't able to catch up that much resource for you. Best option is definitely dedicated server. But VPS is well enough to hold that much. Changing your host to some other shared hosting will not solve the issue.