I want to upgrade electronics on my boat. It is a 31 ft Bertram with upper and lower controls. I like the Garmin Gps but the sonar is OK, but I like the Lowrance sonar but the gps is OK. I'm thinking about the Garmin 540s on the upper controls and the Lowrance LX 28HD on the lower controls. Anyone have experience with either one? I want to know what are the pro and cons of each. I will be fishing for perch, walleye, and muskie. Thanks.