There are too many choices, too many alternative paths to say which are the top ones.
I personally use two programs, a very good mpeg2 encoder called ProCoder and an authoring program called DVDLab Pro.
CCE is a faster mpeg2 encoder with excellent quality output, but costs $1950. CCE Basic works for most people, and is relatively inexpensive at $58, but only allows 2 passes on encoding.
There are some free programs that fit your needs, like Avi2DVD, FAVC and DVDFlick. Avi2DVD can use CCE as its encoder, but not the basic version I believe.
The HC encoder is a very good free mpeg2 encoder, and can be used in FAVC or Avi2DVD. If you haven’t used encoders before, this is where I would start. If you want to try FAVC, I would stick to the 1.04 version since the 1.05 version has shown some bugs with new additions.
Avi2DVD, FAVC and DVDflick will get you all the way from divx/xvid to finished dvd.
Another choice might be TMPGenc Author 3, since it combines their encoder and an authoring program in one. This is a commercial program, but does come with a trial edition, so you can check it out before buying. It has the requirement for periodic license checks, so you would have to install it on a computer with internet access. It won’t be the fastest encoder.