an nice old 4g civic or 2g crx (even a 1g crx) is a good platform...they are cheap and good cars to thrash about as they can take abuse when learning
from what i've seen not all autoxs are the same...there are some with long straights where more powerful heavier cars actually have an advantage and there are the tight twist tracks where the lighter more nimble car will have an advantage...but as mike said the driver is the biggest factor in all forms of racing