Played around with Spectrasonics Trilogy and I found it useful for lots of styles. There has been some talk about rock bass here and I felt I had to do a test. Its just a drumbeat and some of the electric bass sounds. One version is clean and the other one with amplitube.

Imo, works great for rock too!

http://62.13.11.115/trilogy/

Check out a demo I made for spectrasonics.. more to come:

http://www.spectrasonics.net/instruments/trilogy/Trilogy-booty_booster.html

/Tobias