You can check your hostname under Webmin > Networking > Network Configuration > Hostname and DNS Client. Unfortunately, some hosting companies overwrite this information every time a VPS is rebooted - you may need to contact them to get it changed. Choose a fully-qualified subdomain that you own, such as "webserver.mydomain.com" or "mail.mydomain.com". Do NOT accept a generic name provided by the hosting company if you will be sending email from the server because spam filters will block it and you can't easily generate SSL certificates for it.
Keep firmly in your mind the sort of assets that you require to serve your site(s) when seeking a host. Cost in a VPS is important, but not as key as you might think. VPS resource availability is scalable, so the cost that needs to be looked at is comparable cost from one host to the next. Also – as cPanel revised their pricing model recently, web hosting companies across the board will have to pass those costs on to users sooner or later. You will need to consider the cost of control panel when selecting a VPS plan. Companies like ScalaHosting has developed their own control panel to mitigate this issue – so their users would have little issues with the price hike.