Buds Guns seems to have a good reputation with the forums I frequent.
Impact Guns seems to be one of the worst, with slow delivery times and not keeping advertised items in stock.
If you're looking for used, you might have better luck looking at the Auction sites like Gun Broker.
If you find a store you want info on, then I'd join up on THR and do a search. THR seems to be one of the biggest Gun Forums with the most information.
Keep in mind, that with shipping cost and the FFL transfer fee, you might be better off looking for something in the local area.