If I had (4) 6 1/2's and I went to (3) 8's, how much louder would I be?

sorry it cant be that simple but theres going to be ALOT more that factors into that then just speaker size and quantity. its all about brand and model, how much power, what type of enclosure will it be in. you'd have to get alot more specific

And vehicle, driver positioning, etc...

No way to give you a solid answer, best way to find out is to test.

to sum it up... its all in the install. keep on testing.

Thanks for the answers, my intent of this post was basically just to say I was competing again after a year off. My last setup was with (4) 6 1/2's and this year it will be (3) 8's.

petey...what was your highest score last year with those 6.25's???

A 144.5 on the TL and a 145 on the AC.

Got started on the box on Friday and slowly between chores and other things to do it should be finished today. Hopefully the 1st show will be either a USACi event on the 11th or a Clash show on the 17th.