What is the problem with the FlexiPRINT RIP? For me, it have currently one of the best drivers and functionality for that printers. But, to be honest, I too change some default settings to let that software working smooth. And sometimes the new technology of the printers is confusing: blaming the RIP for wrong colours for example is wrong, because the profiles are printer based.
This is a list of the certified RIP's for the Latex Printers:
http://www8.hp.com/us/en/commercial-printers/latex-printers/rips.html
I'm sorry for that Signlab-Spammer, but Signlab isn't certified. But that doesn't mean that it won't work.
At the end the suggestion of dypinc is good: because we don't know what your needs are, you should check yourself the possibilities.