These are the recommendations for the Linux web server where you will have to host your Signal Magician control panel (in the form of a website). Server EA and Client EA will have to run on a Windows VPS or computers.
It is usually difficult to predict exact web server requirements, but here are my general recommendations.
Personally, I use LiquidWeb Hosting, and I recommend them because I am highly satisfied with their service myself.
Obviously, you can use another hosting provider, but with LiquidWeb it is always easy to setup Signal Magician and all the plug-ins that come together.
For less than 50 clients choose the Storm® VPS.
Follow this link to order Storm® VPS: http://bit.ly/liquidwebvps
If you just start with no clients or a small group of customers (below 20) you can go with the cheapest "Storm® VPS" solution $60/month + $10/mo "fully managed support."
For more clients, you should be looking at Storm® Dedicated Servers. These servers run in a cloud environment which is awesome because it allows you to upgrade your server later with more CPUs or RAM.
Follow this link to order Storm® Dedicated Server: http://bit.ly/lwsds
For 50-100 clients it should be enough to have 4x Core CPU server for ~ $150/mo.
For 100-300 clients it should be enough to have 8x Core CPU server for ~ $250/mo.
For 300-500 clients it should be enough to have 8x Core CPU server for ~ $350/mo.
For 500+ clients it should be enough to have 16x Core CPU server for ~ $500/mo.
Whichever you order, make sure you also choose "Fully managed support" as well with the "CentOS with cPanel."