I pretty much went through this thought process over the last year. I'll share what I did, what I learned, and what I'd change.
Garmin also has a VHF AIS (receive only) GPS product - the VHF 215 AIS ($550). I replaced my Standard Horizon with the VHF 215 this season, and it integrated right into my NMEA2000 network, and displays AIS targets on my aging Garmin GPSMap 7212 chartplotter, which allows MARPA tracking, etc. The 215 allows for a helm repeater handset - Garmin GHS 211 - which is fully capable, meaning you can change VHF channels, turn the VHF on or off, change volume, and listen to the handset extension's speaker in the cockpit. That's pretty awesome. And you only need one VHF antenna, and the GPS antenna is built into the unit, which works fine on most fiberglass boats. I don't use the unit's GPS antenna, so I turned that function off, since I already have a dedicated Garmin GPS antenna and unit on the boat.
Two issues here though: 1. Its a wired handset, which cost me $400 to have a technician run to my pedestal (I couldn't figure it out). That's in addition to the $179 handset cost. 2. The first handset I bought didn't pair with the VHF radio because the firmware version needed to be updated. Now I'm a pretty darn savvy electronics guy, but I just could not get it to update, even with tech support help. So I exchanged it, and the 211 worked right out of the box. Garmin was great here.
However, I think wired VHF extensions are old tech in today's environment. Even Garmin admitted they're working to have a wireless handset extension option in their lineup. These days you shouldn't have to run new wiring, unless you're into that sort of thing (which I'm not). So if I had to do it all over again - particularly if I didn't have to consider compatibility with a Garmin Chartplotter - I'd think about a VHF AIS GPS unit that supported wireless handset extensions. The only one I know of is the Simrad RS35 VHF Radio with AIS (receive only). Its actually cheaper than the Garmin at $399, has all the same capabilities, and supports MULTIPLE wireless extension handsets (think multifunctional like walkie talkies for anchoring, etc). Those wireless extensions are $179 each.
And if you use an NMEA2000 network, you can plug in something like the NMEA 2000 Wi-Fi Gateway from Yacht Devices ($200) and now you're getting all data on the network broadcast wirelessly to whatever you want - your iPad, iPhone, etc. I added this also, and am still playing around with it, but I can get AIS on my iPad on chartplotter software. On my boat the older NMEA0183 network is plugged into the Garmin Chartplotter, which is plugged into the NMEA 2000 network and acts as a translator. That means I also get all my data from wind, depth, etc. over my wireless NMEA 2000 connection. Its pretty cool, and I'm only starting to figure out the best way to use it.
FWIW, I think that using an iPad for a chartplotter, while there are limitations (e.g. brightness in full sunshine, battery dying at inconvenient times), is a reasonable alternative to a dedicated chartplotter. The software is always up to date with the good apps (as opposed to paying $300 for an update for your chartplotter every year), and its portable around the boat. I recently crewed on a Hinckley Sou'west 42 from NY to Maine, a boat which has done 2 transatlantic races, a dozen Newport to Bermudas, Fastnet, etc. It has no chartplotter in the cockpit (it does have one at the nav station). But everyone uses the iPad, which repeats the chartplotter in this case. Otherwise there's no nav aids in the cockpit. Another buddy of mine who is an experienced offshore racer has also gone solely to an iPad on his J42 in lieu of a dedicated chartplotter, and another friend has a finicky chartplotter from a PO and has elected to mostly use his iPad (they're headed to the Bahamas as they retire this year). So, for every naysayer, there's a growing number of very experienced folks moving away from chartplotters in the cockpit. If the PO of my boat hadn't put in a Garmin 7212 that's probably where I'd be right now (that 12" screen is over the top, but pretty awesome when I can overlay weather, radar, ais, all at once and it doesn't look cluttered). And that's the one caution I'll lay out - I'll never get my radar to overlay or display on anything but my chartplotter because it requires an Ethernet connection due to the bandwidth. Raymarine may have solved that with their latest wireless technology - maybe someone here can comment.
Hope this helps. If you go this route it'll basically turn into a hobby. Good luck.