I don't really know what your production skills are but there aren't really any "magic" plugins. There are good and really good ones, but most of it is determined by the guy behind the keyboard and mouse.
For vocals and especially spoken voice, proper diction and basic mic technique are more important than plugins. Most mics have a proximity effect which means you get a lot more low end as you close in on the mic. Getting a consistent level and tone starts with a correct performance. It's always better to retake than to fix it in the mix.
If you think you have all that down, basically all you need EQ and compression. You could also use a noise get but although it's more labor intensive, manually cutting out noise between sentences is better. Sonar already comes with EQ and compression. If you want something better or different there are many options, as joyof60 also said. My personal favorite for EQ is FabFilter Pro Q2. For vocal compression I use Waves Renaissance Vox (RVox) a lot but it's pretty specific. Most compressors are more versatile, including the ones that come with various versions of Sonar.