Good info, sam. While I didn't find the Forester seats uncomfortable (I drove an FXT with broken in seats), their lack of lateral support and the FXT's pretty boring interior/instrument cluster have been deal breakers for me so far. Subaru still puts kick *** HK sound systems in their vehicles though. How does the one in the RDX compare? Is the RDX as quick? How about handling? Tight around the curves or no? I test drove one but it wasn't extended enough of a drive to really appreciate it. So I stick with my Legacy until I find something else that pretty much has it all. To date, that's a BMW X3 with the M package (the perfect vehicle IMO), but they're outside of my wheelhouse $.
I like the sound system. I didn't really check out the HK in the FXT during the test drive, but the RDX audio sounds great. It has a nice surround mode. I turned down the center speaker because I found it annoying to have so much sound come out of the center of the dash. Some people might like that aspect. Integration with iPod is excellent. The only other sound system that I've experienced that was better than the Acura was the Nakamichi in my Lexus. That one was simply amazing.
I find that the RDX is very quick. It's rated at about 6.2 sec 0-60 by Car and Driver. I can attest that it lives up to those numbers. It was definitely faster than the 2015 FXT I test drove. The transmission is very impressive. It always seems to either be in the correct gear or shifts nearly instantly to the right gear. If you shift to the "S" mode, the character of the car become very "sporty". It stays in lower gears, downshifts more often, and the throttle response is quicker also.
As far as handling, I think it's very competent and holds the road very well. The steering has a very quick ratio, the car changes direction very easily. Takes some getting used to, since my old FXT needed about a whole extra turn of the steering wheel to achieve the same turn angles.
It grips in turns very well, haven't been able to make the tires squeal yet. Having said that, it is a front-biased car, and you can feel some "plowing" in sharp, high speed turns. Powering out of a turn feels normal. My old FXT felt slightly more balanced in that regard, not sure about the new FXT - I didn't really push it in turns during my test drive.
Since it's front-biased, you also feel mild torque steer during heavy acceleration. It is very, very subdued. I'm just used to rear and full-AWD cars, so this is new to me.
The ride quality is on the sporty side. It's smooth and compliant, but you do feel bumps. It's definitely not "cushy".
Overall, the RDX is very quick and handles well, but all the components work so smoothly together that you need to pay attention to the speedometer because you may not notice just how fast you're going.
Maybe that's why a lot of reviews call it "boring". It just does everything so well that driver involvement is limited to just telling the car what to do and where to go and not really expending much effort on making it all happen. I personally don't find it boring at all. And I've owned a Supra, a Supra Turbo, a GS400, and of course the FXT, so I think I can be a pretty good judge of what's boring.