Sounds like you already have the video on PC via some sort of capture process.
Ulead VideoStudio 10+ will do a great job of capture and authoring DVD's.
But I also find that using a set-top DVD recorder is the easiest way to good quality capture. May of them have firewire ports for direct capture.
Sounds like what you are doing is converting to MPEG then re-coding again in Sonic, which is an extra and un-needed step. Many programs will re-code whether they need to or not, often resulting in larger files. If you already have an MPEG that is satisfactory to you, look at TMPGEnc DVD-Author 1.6 (not 2.0) for a simple authoring process.
The Ulead solution would be for a one-stop capture/conversion/authoring program.