Andy, you will need to use your own local MLS search engine. Maybe pull up tax records. Statewides such as MLSListingsInc, Quattro, and Mercado are likely to be incomplete as well.
I don't think any single site is going to have all the information. If you do the painstaking research yourself, you can be the one to distribute that analysis.
Trulia is a consumer site, it is very good site for drawing consumers to use real estate agents.
Precisely because it gives them a lot of tools and information, but not ALL the tools and information. It is the local agent, ultimately who provides the best value to the consumer and can then reap the reward of the consumers loyalty.