Digital BW, The Print

Sorry if these questions are too "newbie":

 - What is the primary reason for using a RIP Server?

 - At what point in a workflow does one become necessary?

We are finally thinking about shutting down our darkroom and considering purchase 
of an Epson R-2400 or R-1800. For now, the printer would be attached to one 
primary work station (PowerMac G4 dual processor) 99.9% of our work is color and 
printed on lustre papers.

I could see potential in the future for a separate print server, especially if we eventully 
get a wide format printer. For now, I feel a software RIP may not be needed - am I 
wrong in my thinking?

Thanks in advance...