Hi!
I use PowerRIP 2000 with my Epson 1270 (which is almost the same machine, apart for highest horizontal resolution and borderless printing) and I've found it to be 95% accurate when I compare it with the actual lithographic print.
You should keep in mind that most of all Pantone colors CANNOT be reproduced in CMYK prints. Pantone ink are made with a mix of pigments of solid colors that have nothing to do with standard 4 process colors inks. The conversion of Pantone to CMYK colors will almostalways yields to a duller color.
I suggest you to go to a local graphic arts store or to your print shop to have a look at Pantone solid to process book.
Hope this helps.
Jean-Luc