Here's a forum where lots of good info is available. You'll need to register to access the threads.
http://www.amoc.org/index.php?option...per&Itemid=118
I'll give you a quick few things to consider:
1) Narrow down your search to an '06 (last model year in U.S.). They have a bespoke AM center dash/console. '05's have Jaguar switchgear; not desirable.
2) Road noise is substantially reduced in cars with the optional rear seat pkg.
3) 'Assume you've actually driven one, and can live with idiocyncracies of SMG tranny.
4) Make sure car has had it's scheduled maintenance/service/inspections; relative to it's mileage. They are expensive, and some owners have skipped/skimped them.
5) If still under factory warranty, get dealer to inspect/certify and buy extended factory warranty. Not cheap, but good insurance against potential very costly repairs.
FWIW, IMO, that car is the most visceral and satisfying of any car I've ever driven. Period. You will own a rare beauty.