In our local MLS, any member can do a query on any date range of closings by agent. I'd just call up one of your local offices and ask them to print you a report. Specify your search and sort criteria (i.e., narrow down to your city, decide the date range you want, specify listing side) and you've got what you need to start hunting.

Look at how many houses they have actually sold, (and ask whether all sales from the office are listed under the lead agent, which may not be your agent). But also look at things like percentage of list price to tax assessment, and percentage of list price to sales price. If the listings are a lower percentage of tax assessment than others, then the agent may be leaving money on the table (maybe because the sellers wanted speed over cash?). Or if the agent/seller is generally accepting 75% of the list price, that's good to know, too. Also look at some of the old photos/descriptions of the agent's old listings to see if you like them. (That's a fixable weakness.)

I've been going to open houses for over a year now, and there are a few agents who are really out there pushing it for their sellers. We see their names and their ads and their people all over. That's an excellent sign.