2 good looking choices mentioned in this thread
I was on the verge of getting a Garmin 345 with an Aera 660 ($5k + $750), then downgraded that choice to a Garmin 335 ($3K + $750) when I realized Garmin won't talk to my WingX and that I already have an acceptable ADS-B in solution that works with WingX.
Then I downgraded that choice to a L3 Lynx NGT-1000 because if all I need is ADS-B out, that's the cheapest solution. However, it does require a digital transponder. Garmin 327s are now readily available for $4-500. That was the cheapest solution up to that point; about $2800.
Then at SNF I first discovered the uAvionix echo UAT with a show price of $1000. It claims to work with legacy transponders, and it works with WingX. Claimed to be currently available. It also needs their SkyFYX GPS box, which is being redesigned from a box plus an antenna to an all-in-one antenna similar to how Dynon is doing theirs; all the GPS electronics is right there inside the GPS antenna puck. Claimed cost less than $500, claimed availability 4-6 weeks. I nearly bought an echo UAT until I asked the regular price of the box. It was $1000, so no incentive to buy at the show. Total cost here about $1500 and little wiring, no panel changes.
Then I found the Levil Aviation BEACON. It claims to have EVERYTHING in a little shark fin antenna box that goes under the belly. It talks antenna-antenna to your existing transponder. All is needs is power and a cable up the GPS antenna on top. "Coming soon". If it had a price, I didn't record it. So an even simpler installation. Buy one box, put it in, that's it. According to posts in this thread, it's looking like maybe low to mid teens in price when it comes out.
By the time I got to the BEACON, I could see that manufacturers are now starting to ramp up better, simpler, cheaper solutions. By 2 years from now, I expect that the two other options I mentioned will be sorted out & will either work or they won't. I also expect that, over the next 2 years, other manufacturers will come up with similar designs that don't require $6K in panel upgrades.
So, I'm going to just forego the FAA rebate and wait and see how the simpler solutions work out.