My first recommendation would be Linux *cough*
Processor and Ram: It's good to start out small. As your business grows and your needs increase, you can always upgrade. Many people make the mistake of purchasing huge machines with a lot of out of pocket expense, and end up not using them.
Software: Nothing really special to mention with the information you've provided.
If you plan on reselling, you may want to consider getting a Control Panel (cPanel, Plesk, Ensim). A Control Panel makes it easier to delegate control to your resellers so that you won't end up having to do everything for them.
