You still need a tripod especially with a 70-200. Get a tripod and use the self timer it is a must for car photography. IS lens's only give you a couple of stops, bump the ISO up a bit does the same thing but can get a bit noisy.
I can highly recomend the 17-55 f2.8 IS, I use it as my walkabout lens. I bought a couple from Hong Kong but remember the import duty.
A EF 50 f1.8 is a must for the money.