Yea, I've been out of the game for a little bit, but its nice to poke around every now and again
If your only planning on running soloII / autocross, then you wont get much downforce from anything. Problem is, ya have to be doing over 80 mph to see any real gain from wings/skirts etc. Ive seen 700hp cars perhaps hit 65 mph on our local autocross tracks. Now, running hill climbs, road courses or ovals, now all the time you spent playing with the airflow over your car comes into play.
If you want to kick some butt in soloII, make your ride street legal. They will class you with race prepped mini coopers and civics. Go get em!