Asterisk isn’t a “get this size box and it can do x calls, and this size box will do z calls” sort of software. It’s a development environment.
It’s rare that anyone can answer a call like, “What would it take if I wanted to do this?”. Most people are building systems with Asterisk for the first time, and no one is really going to have any experience with how anything will go.
It really depends on what you’re asking it to do. Playing messages is a processor intensive thing for the system to do, so it’ll take a few processors.
For example, you can put three or four servers to the task, each checking a MySQL database full of numbers to call. The servers can then update the database to let you know if the call was answered, busy, SIT tone (disconnected line), etc.
It’s really up to you to develop the solution you want. Just rememeber; It’s your solution. You’re going to build it, you’re going to have to support it.
50 calls worth of internet bandwidth might be a bit expensive though. You can get that (48 channels) with 2 T1’s. If you use a Dialogic card with DSP’s, you can offload the processing necessary to play the announcements to the Dialogic card. If you do that, you can easily build just one server to place that many calls.
You might just consider using T1’s instead of a VOIP provider.
Click here for a handy bandwidth calculator:
asteriskguru.com/tools/bandw … ulator.php