I am running Avast, Secunia PSI and CCleaner on a regular basis. Do I need a program like SpyBot also?

Each software program has its strengths and weaknesses. Spybot is very good at pulling out many different spyware programs, i would suggest running it every so often to make sure the others dont miss something. I would not suggest running its real time protection if you have defender and avast installed.

I should add that I also have windows defender running daily.