Those are great cars. My Dad has put over 200K on this 94 Q45. Only thing is to do some research on that Active Suspension. I think I've read that the Q45As had some problems with that, and its not cheap to fix. Those are great engines, and with a V8, you'll know it'll last a while.
We've only had one or two problems with the car, and nothing major. He had a WP Pulley seize up and break the bolt, and there is something wrong with the Bose stereo, but other than that its great.
You DEFINATELY need winter tires for this car too. Its not the best in the snow. In fact, it can be a little scary at times.
