Hello jotapeh
To have ran a MUD (Multi User Dungeon, or online text rpg) for 15 years and worked 6 years in a company doing online games, here is my advice :
You don't need to bother with a server deployed over several hardwares or even several threads for something under 200 connected players.
Some muds run very well on a single thread with 100+ players. Mine worked fine back in 2000 with 50 active connections. With modern hardware, this limit would be multiplied, should muds could attract thousand players.
Consider also than MMO surveys show that only 10% of an active player base is playing at normal time. It means you wont have to bother until you have like a player base of 1000 or 2000 active players.
My advice is to make a simple server without to worry about supporting thousands of players until you get at least in the alpha/beta and you get indeed a community of thousands of players.
You can check one of the many open source MUD engine to get a basic working server network layer. You would find eventually links to source codes at the
http://www.mudconnector.com site.
Modern dedicated linux server can be rented at 30$ a month. You will be able to do more things by yourself than what playerio offer, like email for your players and hosting your website and your forum.
However if you need one day a better server solution, consider than the money generated by 2000 active customers could allow you to hire a competent network programmer to make the work. At this point you could have to refactor your code so it works over a distributed architecture.
Now, if you want to save time to proceed quickly to the point you implement your gameplay, you can indeed buy a technical solution. Don't forget that no company selling middleware or hosting solutions is immune to a bankrupt. One day, the company hosting your game can close and you will have to redo everything somewhere else. The worse thing could be to see your game closed without the possibility to get a back up.
For online games i suggest strongly to host your games on your own server where you can organize back ups so you can rebuild another server on any lambda linux solution in a couple of day with a loss or 1 day of datas.
For langage, i would suggest indeed java or C++ for the barebone skeleton of your server and, if you feel comfortable with it, a scripting langage for the gameplay. Many affordable MMO solutions use this idea. Personally i go for pure C++

Consider than the network layer and the message dispatcher must be the most quickly. That's why i would go for C++.
Again i suggest to look at the mudconnector site and inside the various MUD open source engines. You will find here several implementations of a network layer, a message dispatcher or a command-line interpreter, session managers and message-to-X players solutions.
Also, most of the MUD engines are C ANSI/C++ standard/java and compile under linux as well on visual C++.