Hi, just thought i would share my experience with my SE-L. Really great and very smooth car on the motorway. Living in central London, there are hundreds of road humps that I find the air suspension to not absorbed them smoothly. I also had to change the front passenger side suspension as I would hear a knocking sound when I go though humps. Lucky for me, found second hand one.
My advice to you is find the SE model as other members have mention.
I've also put 235/60/18 which are smoother to the OE 235/55/60
Had my RX300 for five years and never had problem with the engine. Really great car