I have not examined all the most recent gadgets in detail so my recommendations are general. First you need to check what frequency-ranges you are permitted to use in your country/area, and if a license is required to operate radio gear other than the most common consumer gear. Next I would look for a kit that offer a digital link. Digital adds a little latency, but it is unnoticeable with the most recent circuit designs. Digital also has the benefit of improves scrambling (over analog) and even digital signatures in case you are concerned about security (someone/something messing with your performance). Shure ULX-series are units that meet these requirements, but I haven't had the opportunity to test any of them yet.
As a G90 user I have no problem recommending that if you and everyone else nearby can live with its limitations in terms of 2.4G interference. I've seen 2nd-hand units being sold for very reasonable prices.
I have extensively used both the line 6 and Shure digital wireless products and can say emphatically that the Shure system plays much nicer with nearby 2.4Ghz radios like WiFi, in fact since switching to the Shure I have had 0 interference issues and I had many in both directions with the Line 6 radio.