There are several good stores in Montgomery County. Some of the small ones do a good job keeping their prices down. I frequent I believe it is, 6 different ones in the general area.
However, Congressional has a wonderful shop and fantastic quality stock and staff. They have been very helpful and they keep a super clean shop and great variety.
Another store that I frequent that I have found to be of superior quality and knowledge is Scales Tropical Fish Warehouse (don't let the "warehouse" in their name throw you, it's far from a warehouse). I would say it is easily on the same level as Congressional

. I know for a fact that they quarantine all their stock prior to releasing them into their display tanks for sale. I have had the priviledge of visiting their quarantine area to pick out a few fish for purchase after their quarantine period but before they were out for sale. Granted their floor display is not as numerous as Congressional's, but if you have the oppurtunity it might be worth stopping in. Depending where you are coming from this might be closer to you. Not by a huge amount but ....
Here is a link to their site:
http://www.tropicalfishwarehouse.com/
Between Congressional and Scales I purchased just about all my fish and out of the 5 Angels that I purchased from the two stores I now have 2 mating pairs.
Looking forward to hear about your next visit.