Planning for SUN server

How do we plan for hardware on SUN Platform. Rather any platform.

We are thinking of an e-commerce application witn SUN Solaris server and Java web server.

We are expecting around 10000 hits per day.

I know about how to plan for the bandwidth required for 10,000 hits. But how do I plan for hardware like

No of processors
RAM required

Generally what is the industry standard for calulating the hardware required depending on the no of hits that will be received on the web server ?