I have a Standard Horizon CPV350. It intergrates everything into one great package. It's a 7" gps, with integrated vhf radio, and I have also added the sonar module which allows you to switch from gps to fishfinder, or split the screen with both. Keeps the dash and front of the cockpit less cluttered from having separate units mounted here and there, and it's very nice to have everything right at your fingertips in one unit.
The sounder module runs at 50 or 200 khz, and the detail is amazing. With a properly mounted transducer, I've had no problems losing signal. So far I've been up to 25mph and not lost bottom at 490'.
I've got a cmap max cartridge in it for charting which covers the west coast from Puget Sound to Alaska. Super detail on the maps right down to the individual fingers of the docks at many popular marinas. It will also display tides and currents, and list the details of every bouy, light, or marker. All really helpful for a boating novice like myself.
I am really pleased with this unit, and am still finding more things it will do.