To start up, do some research. Get a network that can handle huge bandwidth requirements, make sure it is a totally reliable network.
There is nothing worse then an overrun network causing streams to buffer every 5 seconds or a network that is down 5% of the time.
With regards to server power, it doesnt matter much, a P3 will do nicely. With regards to server admin, its all quite basic, but if you are not competent on a server, learning how to run the DNAS itself will take 10 minutes or so, but get a professional in to harden it and keep it running sweet.
If you are using the servers solely for shoutcast though, you dont even need Apache running, and you should never really see any load at all on the CPU and the server will generally run sweet 24/7.
Dont compete on price, if you do, you will kill yourself straight away as the pricing within the industry nowadays is stupid.
I have had 3 customers sign up this month as a direct result of very cheap companies not being able to proivde the services they paid for.
Also, I wouldnt recommend doing what a lot of cheap companies are doing and hosting the streams on a web hosting server, get a server that is dedicated for shoutcast and nothing else.
Finally, get either a huge bandwidth level or a unmetered server, as shoutcast WILL eat a HUGE amount of bandwidth and data transfer.
There are a few companies offering shoutcast reseller plans nowadays, you may wanna check em out, but again, make sure its reliable.