I have a 99 RX300 with a Sirius set up. Over 2 years, I have received excellent service and performance from Sirius.
Like SW, I mounted the unit inside the console at the front (can be viewed with the drawer only slightly opened) of the top drawer. The receiver is mounted under the drivers seat and the antenna is mounted at the rear of the luggage rack and blends in with the rack.
From the interior the vehicle looks stock. My only improvement, which came out AFTER I purchased, would be having the unit that can be removed and taken to your home stereo.
The real mystery to me was the need to include a remote control for the stereo. It made sense when my 11 year old daughter took one look and exclaimed "great, now I can control the radio from the back seat. Shortly thereafter, the remote vanished ;)
Nick
Las Vegas