Hi Gary,
As I wrote in a different thread, Sonar X1 has many harmonic exciters in the box as it stands: It has the harmonic exciter from Project 5 (now for 64-bit usage), the VC-64 can add saturation which adds harmonic content, as does the vocal and percussion strips (saturation modules), the Tube leveler adds various amounts of dynamic saturation, the Pro Channel has it's Saturation module, and the Gloss EQ is a form of high frequency harmonic excitation (if that's a real word). There are all sorts of effects to be found in Dimension Pro and Rapture LE for adding harmonic content to a patch, and Z3ta can also be used as an FX plug-in for any track.
You can purchase the BBE Sonic Maximizer from Nomad Factory, or check out what's offered at Voxengo (excellent plug-ins for Sonar's 64-bit throughput) , or the PSP audioware (Vinatge Warmer2--also top notch).