Da taada da.... I'm here to direct the TARDS lol.....
First of all..... DIY PA is harder than DIY home.... For several reasons. First off let me ask some simple easy to understand questions for all the little kiddies out here....
1. How much are you getting paid?
2. How many people are you going to be covering?
3. Where do you live? (This affects the type of music you will be listening to)
4. Will these be "upscale" events or "back yard" deals?
5. How often are you going to be moving this stuff around?
Ok, so why do I ask the questions I ask? You have to factor into how much you are making for the budget you spend on your PA. If you make 15k a year you wouldn’t buy a 50k PA like a curvilinear line array with subs. Second, if you are going to be covering 20 people you don’t need as many boxes as you would if you were covering 200 people. That said no two jobs are going to be the same so you want the system to be build able, meaning for one job you might use 2 high boxes a side and a sub, but for another job you might only use 1 high box a side and no sub. There is no point in dragging PA out that you don’t need to use. Third, if you are going to be playing rock and roll dual front loaded 18”s, stupid wedding music 15” 18” hybrid box, rap you need more subs. The Pro Audio and sound reinforcement world is completely different that the car audio world. I know you said that thing about using car audio drivers, DON’T. PA drivers are made for PA applications; car audio drivers are made for that application. Think of it this way, a PA driver that weighs 15lbs vs. a car audio driver that weighs 50lbs now put it in a box that weighs 50lbs. Which would you want to move if you had two drivers in that box? I know that everyone on here is strong into the DIY, but for Pro-Audio to do it right I wouldn’t even touch DIY. You need something with a good strong horn and a good 12” for your top box. You want something with a solid dispersion pattern around 60x40. (DIY you would never be able to match that 12” and the horn). Subwoofer wise, depending on your needs I would say either a sub with two 18’s or a 15 and a 18. I will post some links for you to look at later today.
But, I am also throwing this warning out to you. There is a lot more equipment that you need than you think. You are going to need a mixer that is good first off, wireless mics are not cheap, I would get two compressor/limiters for the mics, and EQ between the mixer and the speakers with decent processing in it, all your necessary cables, including correct power. If you go unpowered you will need to get processors if you go powered cabinets they will be more money….
I will send you some links….. Good luck is all I got for you…. It’s not as easy as you think…
Also, what are you going to be playing the music to the system with? If it’s a laptop think again unless you want a really good mixer and a few DI’s in-between.