RIP = Raster Image Processor. Specifically I was talking about a software PS RIP (otherwise you're definitely not getting anything cheaply)

I am pretty certain that I saw something for use with ALPS printers specifically. But even if not, there should be solutions that are not printer-specific and work in conjunction with your Windows-installed driver. Very basic: it takes in post script, rasterizes it, spits it out as a bitmap. The solution, ideally would sit on your PC and allow network connectivity (it would be pretty useless for prepress use if it didn't). Now, since i'm not mentioning any specific products this is all very general. You may have very well set up the best solution from a cost standpoint (free) I don't know that you'd be able to do any better (or more convenient) without paying for it. Not to mention that a given product may be crippled in some way that would make the solution less than ideal for you. And the fact that some RIP solutions offer all sorts of goodies like colour management, anti-aliasing, optimized for large-format, etc..

I just checked ALPS' site and sure enough, there's a software RIP in their accessories section. Like almost everything else on their site, it seems to say it's discontinued. And for some reason it says Mac-Only on the first line and then says Mac/PC in the body.

Bruno