Well I'm pretty sure that some of the mods I've already done to my car puts my car into a somewhat hard/high(?) class (LSD, coilovers, various suspension components, etc) So even what class I'd be competing in is already limited. And to be honest I'm not really concerned about how I do in the class, just being able to run is fine. I can't predict the future but I would like to do more than just the local autocrosses.

Are the rule books online somewhere I could look at? That's my biggest concern is that the cage is approved in a certain class for the local autocrosses, but when I decide to go to a track it won't be legal and I won't be able to run.

The reason I just haven't gone ahead and gotten an Autopower cage is that I've heard their fitment is less than optimal. In addition the Cusco cage is bolt-in. Which is good in the event some place complains I could just take it out. Check the link I posted, it has pictures of the cage in question.