hey parco,
Are you not satisfied with the Waves S1 ?
Personally, I have the Sonalksis Stereo tool (which looks like the S1) and when I demoed it, I was very impressed ! It's considered as the best stereo tool plug and it's true theat Sonalksis is well famous for the undeniable quality of their plug-ins ! By the way, I 've compared with the freeware Flux stereo (whose name is also very famous in the audio plug-in world) and it appeared to me that Sonalksis was superior.
But as the mixing tasks proceed, projects after projects, I realize that the Sonalksis couldn't be put directly on the Master bus with this magical effect confering instant and gratifying wideness to the entire mix. (although with subtle settings, the Sonalksis do bring something in comparison with similar other plugs). I mostly use it on bus for widening a reverb, background vocals, violins and synth pads... But I imagine you can get similar results with the S1 ?