Yep, did it for a couple of seasons when I lived in Montana. Haven't been able to do it since then. In my region my ST was pretty competitive. However, when I raced against WD40 in his SVT, he crushed me. I would like to blame it on the shitty tires I had, but he was also just a much better driver than me. Also, focusedaddiction had a pretty heavily modified ZX3 and would beat most of the field.
Is this sedan your current car or are you looking to get a track only beater? If you're talking about your current vehicle, just go with it. The experience you gain will be invaluable. After that, you can figure out which cars are most competitive in their respective classes, and set a goal from there.
I never wen't to an auto-x event seeking to beat anybody other than myself (well, maybe focusedaddiction and twerpie1).