AVG doesn't alter anything if I leave it checking my emails, even with B9 switched on
That is because it doesn't scan your email before it reaches the inbox, so any potential virus is already on you system. B9 (and avast) realise that is not a good idea, so they intercept email and scan it before it gets to the inbox.
Don't throw out the baby with the bath water, avast is far better than AVG. I know I used it for more than 18 months and got totally fed up with its interface and its cr*p updates. It really doesn't hold a candle to avast, it doesn't have any means of doing a boot time scan (win2K/XP), protection for IM, P2P and is much more flexible than AVG. When I switched to avast, on the first scan after installation it found two viruses that had hapilly resided under AVG for god knows how long.
These forums have many, many ex AVG users who are more than happy having made the switch
Oh and try getting any help or support from AVG, no chance (no support for free version), unless of course you buy the Pro version. You have probably had more of a response and help whilst trying avast than you have ever had from AVG.
You can probably see the kind of people that frequent these forums, they have a common purpose to help other avast users get the best out of the product. For the most part these people are just like you and I, avast users. There is however, excellent support and help from the Alwil Staff who are regular contributors on these forums and very quick response to suggestions, etc. You really can't put a value on this but it is just one of the things that puts avast head and shoulders above avg.
The alternative as I see it is simple, don't use avast for your mail scanning, leaving your mail account settings set-up for B9 and allow B9 to look after your email. If an email contains a suspect attachment which B9 changes the filename and you still insist on opening it (after renaming it by removing the .b9), save the attachment to your HDD and scan with avast before opening.
The Standard Scanner can have the sensisivity set to high and scan all created/modified files and this would also pick up potential virus infection