Other free firewalls could be used in conjunction of avast.
I think it will be better if you use this way. An all-in-one-systemworks-like-application is on the opposite side of th
layered defense, which is usually the best solution.
avast and ZoneAlarm, or Sygate or Agnitum Outpost or Kerio... you will be protected, in my opinion, in a better way than a single integrated application like Trend Micro.
Consider too: updates and support