Some of the answers you've already seen are very good. I would however say that you cannot judge which agent or firm would best serve your needs based on this kind of a search. To find an agent/firm that would best assist you, you really need to interview several of them in person and determine who you feel comfortable can then meet your personal needs.
Some agents work with a lot of buyers, such as myself. So to do the search recommended by some of the other agents on here, may not bring up those agents names. There are agents such as myself who keep a fairly lean listing inventory, feeling that they'd like to continue to offer their clients that hands on personal touch that can only be afforded by not taking on more than one can handle. My husband and I are out at our listings 1 to 3 times weekly checking on things, such as the brochure boxes, disclosures, sign in sheets, making sure that in the case of vacant homes the water heaters and/or pipes haven't broken and spilled water all over, thermostats are being kept at correct temperatures, doors locked and lights out. Things like that so that we can notify our sellers right away if we come across any problems.
While a firm's support of it's agents through the resources they provide their agents can be very beneficial to a seller and buyer, it is generally the individual agents that sell the homes. I often tell sellers who comment that their agent hasn't shown their home one time, or very few times, the listing agent statistically won't be the agent who sells your home, the buyer's agent will. If you are getting a number of showings, then your listing agent has done exactly as you have asked them to do and gotten the word out to those buyer's agents, so that in turn they are bringing their buyers out to view your property and you cannot fault them for a job well done. On the other hand, if your property is not getting the showings you believe it should, then it is critical that you contact that agent and discuss reasons that they believe it's not showing. A good agent should be able to show you what the market trends for showing activity are and also offer advice on ways that you might overcome any obstacles to ensure that your property starts getting the maximum number of showings possible.
If you like further information, please feel free to contact me.