[url=http://www.thegpsstore.com/Standard-Horizon-Matrix-AIS-GX2150-VHF-Black-P3711.aspx]Standard Horizon Matrix AIS GX2150 VHF - Black The GPS
Thats an AIS receiver only.
Which, imho, should be banned, outlawed, and chucked overboard. I think the benifit in them is others, bigger and faster can see where you are and what you are doing.
Mind you i think that unit is fine IF one has an AIS transponder.
The radar needs the Lowrance plotter, which the OP has, so a cheaper AIS transponder will come in under the $2,000. But for people who need the display too its much more expensive.
Most AIS transponders are stand alone and can integrate into a PC running OpenCpn, for example, so the total cost is just the AIS box and $70 antenna(and its GPS antenna).
If the budget extends to it, buy it. Buy everything, buy a bigger boat etc.