SpyBot - Spyware Blaster - IE SpyAd difference?

Greetings.
So far, I've gone back 3 months in this NG to see what is said about SpyBot,
Spyware Blaster and Adware. In reading, I find something about IE SpyAd.
Getting too many things clashing in my brain. Will someone inform me the
effectiveness of these programs in comparison with each other and why some
are used in conjunction? What I have been using, and still am, are Spybot
1.2, Ad-aware 6.0 (keeping both updated) and just 2 weeks or so added a Host
file manager suggested by Silj & Drapper Dan from here referring me to
website http://mvps.org/winhelp2002/hosts.htm.
Questions:
1) The new version of Spybot, as I read it from the website, uses Host file
feature. Will this eliminate the use of the Host file manager?
2) Spyware Blaster & SpyBot is said to "talk" to each other yet they do the
same function. Only reason I've read so far here why anyone is running both
is because the databases are updated on different dates. Seems like Spyware
Blaster has a bigger database than Spybot. Are they redundant?
3) What does IE SpyAd do and is it used in conjunction with all above?
4) Is Ad-aware needed any longer with all these others running?

I've never noticed SpyBot in the startup group, yet it often times catches
Ave.A cookie, or something, and I never turned SpyBot on manually anyway. I
don't recall seeing how to turn it off to see how much system resources it
uses. Which leads to the last question.

5) If all of these are not needed, which of these configured together would
have all around protection and use the least amount of resources?

Thank you all for the information in the past and what is next to come
*smiles*
Have a good day!
B.rgds,
Kevin