I did use SpyBot S&D until I figured out it is useless. SpyBot is one huge resource hog and could cause conflicts with avast. May I suggest sticking with avast, MBAM and SAS. avast has no issues with either one.
http://filehippo.com/download_malwarebytes_anti_malware/
http://filehippo.com/download_superantispyware/ 