My Astons have all been used. I've restricted myself to driving a car once and once only, either a single race or a championship, until I hit 100% complete, then I'll go back and tidy up in places where I left easy points behind purely by having forced myself to use a low points car e.g. Sport Truck races, where I used 3 different trucks, instead of going for all 200pt races in the Dodge Ram. Don't ask, I'm just weird like that.
Then, going back to the Heavy Luxury Cruiser, I'll just have to shout Jaguar S-Type R. The thing has grunt (550Nm of torque, stock), and, together with the Mercedes SL600 (R129) has that super-quickshift transmission, which shifts better stock than tuned. Plus, it weighs a round 1800KG stock, which is very neat if you're after points (400HP on 1800KG), and it handles good for such a whale. Now on offer, complete with Jeremy Clarkson effect on the 'Ring.
BTW, I'm finally officially in. I won't make the 111,813, since I'll never have time to get to those 6hours-or-more endurances, but I'll do my best having fun. Perhaps 100,000 is in sight? I'm currently on 7978 points with only few missions done, and most races done in a way that should not be mentioned in this subforum - but the hint is: I lapped the whole field twice in a 7-lap race at Hong Kong. And most of my completed races don't have any points.
And concerning "Gem-cars"... So far, I found the following common attributes common to "gems": They're either
very heavy, not-that-powerful (HP-wise) but with lots of torque (Jaguar S-Type), or very light and less-powerful (GSX-R4) - and either way, they handle better than the rest of the competition. I wonder if two identical cars, PTW wise, but with different torque would get different points...