We’ve got to stop meeting like this! 
When you’re viewing A-A’s log, there should be a button to “clear log”, or something to that effect. Normally you’d only want a record of the most recent scan anyway. I just checked to see if there’s a setting option to overwrite exisiting logs when a new one’s created, but couldn’t find it. (Which doesn’t, of course, necessarily mean it’s not there.)
As for other anti-adware, you’ll get all kinds of answers on that. Ad-Aware and Spybot S&D work differently and at least to some extent are looking for different things, and quite a few people happily use both. I personally like SpywareBlaster and SpywareGuard, both from Javacool – neither one is a scanner, SG blocks in real-time roughly analogous to avast’s resident protection, while SB sets “kill-bits” in the registry to prevent installation or running of known baddies.