I have not used Stylus RMX nearly enough, still learning actually.
but with Omni, Trillian and stylus - you can throw down a serious song track.
I have Reason 7 and with Stylus RMX I have been able to save a REX file and inport it into Stylus to use my own sounds. it's not a simple thing to do but it does work once you have it down.
reason I mention it is that it can expand Sylus RMX using your own sounds, samples or converted samples.
make sure if you are buying a used copy of Stylus RMX that you are getting the Expanded edition that is newer. TONS more sounds and grooves.
I love my Spectrasonics stuff. eager for beginning of May to start playing.