Best Car?

Any thoughts on the best car to have in the game?

Best class A Car? Its pretty diverse now...There isn't really the best. There are cars that make the record lap times, like NSX and Ferrari. Go to the racing page and look at the statistics. Choose which cars score the fastest laps.

it depends on the track

This one; http://www.torn.com/iteminfo.php?XID=519

The Bugatti Veyron. But wait there is only 1 and I have yet to race against it.

Once I finally got some points, a Honda Accord with only handling/braking upgrades cruised me through Class D.

I was smart enough to save some points for Class C and taking the same path in my Honda Integra has worked pretty well so far as well.

Dat Honda handling FTW. :P

It is key that once you start dominating your class you start saving up points for the next class. Class B and A were the hardest. I was able to dominate class B with the corvette once. Once I got to class A I had about 180 points to start building up and yet it took me more than a month to start dominating that class. It is still hit or miss. 

The Ferrari 458 and Honda NSX are the most balanced cars in Class A. Acceleration and Handling are winning on the new tracks for the most part. When you get to the point of being able to max multiple cars, it is important to have different cars prepped for different tracks, though. A Honda NSX set to full dirt isn't going to win on Sewage, nor will a Ferrari 458 set to full acceleration win on Speedway. Those are just 2 examples out of many.

Best car cover's 4 tracks with same set of upgrades.

Honda NSX (A Class)
long ratio, all tarmac
tracks: Commerce, Industrial, Sewage and Meltdown.