To answer your original question:
No.. if you're bashing DON't get a top of the line car. Why? Because they're tuned much harder. As a result, if you crash into anything, chances are you'll need to start replacing parts. These cars are designed to go FAST on a track. Little stones/sticks etc WILL quickly ruin belts and gears.
Oh course, the more you pay, the faster the car and more responsive it will be. The cars that race in MODIFIED easily hit around 80Km/h on many tracks.
As for off-road... no. There aren't really any kits that have the scale look that you want. Some "rally" kits can go offroad, and still look like a sedan. (Eg. subaru imprezza) but they can only handle very little bumps. Ie. can't drive off your kerb.
If you're bashing, stick with a cheap kit.
Untill you have a buddy to race against, you'll be fine. But it does get old if you're by yourself. If you have time, go see a race at a track. It's hard not to get bitten by the track bug.
Lots of set-up, tuning and funky stuff to play with, and the cars are FAST...
hope that helps..
Cheers..