Just to emphasize what Jim said...the styles paks do NOT contain any new RealTracks. They simply combine existing RealTracks into new sets or styles.

There are a couple of things to understand here...

1) if you have all of the RealTracks then you could create any of the styles yourself by simply combining RealTracks and saving as a style but it would take a lot of time to do so. in that sense the styles paks represent a huge shortcut to finding great combinations of RealTracks that work together as styles.

2) if you do not have all of the RealTracks you may find that some of the styles in the styles paks do not work for you because they depend on those missing RealTracks!

My opinion? Buy all of the RealTracks and buy all of the Styles paks!