A good friend of mine just had ADS-B installed in his Citabria. He went with the Garmin GTX-345 and it works great for him, it displays traffic on his Garmin aera-650 and his Ipad with foreflight, his total cost pre-rebate was about 5k. The installation on the Garmin is well known and fairly straight forward, which saved him some shop time. He also didn't have a WAAS GPS source, so that includes the antenna and install for that.
Another fellow wanted ADS-B in his Cessna 182, so he decided to buy the Appareo Stratus ESG. Total installed cost pre-rebate was about 4k. The install is not as well known, and apparently is slightly more complicated. Keep in mind the ESG is ADS-B out only. He then bought a stratus 2S for ADS-B in (another 800 bucks). So he ended up being about 5k total cost for in and out.
My personal opinion is that I am going to wait until 2019, under the assumption that the technology will either get better or cheaper or both. If my transponder quits, I will install sooner.
As for your options, while it is the most expensive, the Garmin GTX-345 seems like the best deal. It gives you reliable ADS-B in and out, without any other supporting devices or complications. It is a known entity, a known company, and a known product. Any avionics shop will be able to install it without issue.
I would stay away from the Nav-worx box. I have heard only bad reviews.