Adware 6, or Adware SE Personal should be ran as a companion to Spybot S&D. Each one may pick up what the other had missed.
Adware/Spyware programs are like AV programs....very few people actually writing the code to keep our PC's clean and safe, compared to those that are writing the spyware/virii. Each company focuses on certain aspects of PC security, so having more than one spyware program installed is a good thing.
Note: Having more than one AV installed is not a good thing.