Another option, if you don't mind not having the TX ability of AIS, is the new Standard Horizon Matrix 2100 AIS VHF. It is an AIS receiver and full featured VHF all in one unit. I just got mine the other day for $326.00 at Defender. Needed a new VHF anyway, hated my Uniden, so the extra $125.00 +/- dollars seemed like a decent price to pay for AIS receive.

Ideally I want both TX & RX but I'll wait till the price comes down and features go up... For now the Matrix 2100 seems like a good entry point for receiving AIS signals and supplementing my radar..