I think you're confused about the technology. XEN/OpenVZ is useful if you have a single server that you want to split into multiple virtual servers with various usages (or just different owners). It works best on high-end systems so that all the virtual servers have enough resources to operate at the same time.
It sounds like you need to choose between buying a low-to-mid range server and hosting it yourself (no VPS technology required) or spending cash on a monthly plan for a server - it'll be a VPS but you'd never know and there's no VPS configuration you have to do. Choosing between those options is a different and better question for what you're trying to do (and one I have an answer for if you happen to ask it on Gaming.SE).