Ahh the mysteries of windows startup, there doesn't seem to be any hard and fast order, it is almost random unless you use something like startup delayer as mentioned. However, I not so sure as to its effectiveness at delaying all startup programs.
I ended up disabling my firewall completely at boot because it has in the order of 750-800 file accesses during boot and avast scans every one of them, slowing the boot. I start the firewall using a batch file after boot when it only takes about 8 seconds to start and have avast still scan the file accesses.
To my mind this is not an avast issue rather the unbelievable number of file accesses by the firewall (Outpost Pro), despite many emails and posts on the outpost forums, they still haven't answered the simple question, 'what files does outpost access on boot and why?'
So rather than delay all the others, you may think of delaying avast to help with boot times, but that does leave you a little more vulnerable allowing a potential threat to get established before avast starts.
So you may well be better leaving the boot sequence to windows.