If I were you I would buy the Standard Horizon unit and sell my Icom unit. This will be cheaper and you will have one less piece of gear to install, power, maintain, and learn to operate.
The Sh radio is under $350.
Thats receive only, btw. Not a transceiver. Also, the $350 is deceptive. You also have to buy the following if you're replacing out a VHF...and like most people, I'm assuming he has a ram mic @ the helm.
Ram Mic to work with SH $100
Cable to extend Ram Mic $25
NMEA cable to work with plotter $40