There is no such thing as a “deal” when it comes to Garmin products through an authorized dealer. Garmin dealers are bound by minimum advertised prices. That being said, the dealer can offer certain incentives which cut into their profits. Garmin also occasionally runs specials that the dealers can pass on to the customers.
The real value is in customer service both before and after the sale. The cheapest dealer will not be the best performing in this area.
A dealer willing to go to bat for you on a warranty claim or send you a loaner, help you troubleshoot issues etc. is worth paying a few more bucks for. Some dealers are little more than a Sears catalog offering little value to the customers.