Difference from stock and pro stock:
You will be defined pro if:
• Competitor works for a car audio dealer, manufacturer or distributor, or has worked for any of the aforementioned at any time within 1 year of the competition date.
• Competitor receives financial compensation for using a specific manufacturer’s equipment
• Competitor receives free equipment or equipment for less than 50% of MSRP from a reseller and/or manufacturer
• Competitors immediate family member(s) meet(s) one or all of the previous conditions
If any of those are you, then you'll have to be in pro stock. If not, rock on in the stock classes. Also...if you meet any of the above criteria and are deemed "pro", then you cannot compete in Street Beat 1-4...you will be automatically placed in SB5
If you'd like more rules details, it's available in PDF format. Go to this page, there is a breakdown of certain classes
http://www.soundoff.org/rules.htm Then click on Outlaw SPL Rules right under CompetitionRules 2009 for the detailed PDF.
Have fun and kick some azz.