No sam I think you will find almost everyone will tell you that running two AV's as real time will cause you conflicts.
Really my friend you are best off running the Avast as your main suite and just using the free version of MBAM SAS and that Spywareblaster which looks to me to be a pro active for want of a better term application - as I said last night I would personally ditch it and then use it if you felt the absolute need to.
If you feel that you have something on board which the others have missed then there are plenty of use on demand scanners to choose from that will not conflict with your main AV - Avast.
Just as matter of interest I always set my MBAM scan up by not including th e File system as in my case Kaspersky does not like it and it takes a while longer to do.
But hey I think you are doing just fine as Brink always says the dumbest question is the one that doesn't get asked