The first-generation RDX (2007-2012) had reliability issues. The current one (2013 and up) had some common problems the first model year, but nothing serious. The one I recall involved driveline vibrations, one of the things many people accept as "normal." The 2014 and 2015 have both been reliable. I'm not a big fan of how the current RDX drives, but many people seem to like it. The Lexus NX feels sportier.
I like how the Lincoln MKC drives a lot, and it has good seats, but less rear seat space than the NX or RDX and initial reliability hasn't been good.
If you can get one under your max, the Volvo XC60 is worth a look. Great seats, comfortable ride, and those as old as the 2013 have been reliable so far. (We have any iffy stat for the 2014, but it's based on a small sample size.) For 2016 you haev to get front-wheel-drive for good fuel economy. For 2017 the efficient turbo four-cylinder finally will be available with all-wheel-drive.
Among regular brand crossovers, you should at least take the Kia Sorento for a test drive. It rides and handles very well for a midsize crossover. Initial reliability hasn't been good, but if the past is any indication Kia will sort initial bugs out pretty quickly. Care from late 2016 or 2017 should be better than those in our survey. (I have more faith in Kia quickly working bugs out than I do Ford / Lincoln.)
Bottom line: you could end up very happy with any of these, but the Lexus is probably your surest bet