heyy man, you have many choices, try go to your local shop and look for some equipment, tell them you want to hear them.,
most cheap/low end subs doesnt play that well.. try stick to brands like cerwin vega, jbl, db, kam. i have 2 cerwin vega 154 the old series, in a ported L design, and its sick. those subs have been measured up to 170DBS! im just saying:D every pa setup is good. its all about the box.. try buy a sub and build a enclosure for it