QTR-Quadtone RIP

I have used (and greatly appreciated) profiles from QTR Create ICC in 
conjunction with standard Epson drivers.  But I am unclear about the 
role of profiles from QTR Create ICC when used in conjunction with 
printing through the QTR RIP.  Does the curve creation and 
linearization of the RIP somehow eliminate or supplant the need for a 
profile?  If so, how is softproofing done in PS?  If the ICC profile is 
still used with the RIP, how is this done?  It seems to me that the RIP 
is simply creating a linearized output (at the printer) and that an ICC 
profile is still needed to characterize that output to eliminate the 
significance of workspace in PS and provide a screen match to print. Is 
it enough to simply use the ICC profile (of the linearized output) for 
softproofing in PS and then print through the RIP without specifying 
that profile?  I'm finding myself coming up short on the concept here.

Many thanks,
Walt