Here is a chart that gives you relative cone size.
Diameter of speaker*|*Cone area of speaker in square inches
18"*--->*254
15"*--->*192
13.5"*--->*143
12"*--->*113
11"*--->*95
10"*--->*79
8"*--->*50
6x9*--->*42
6x8*--->*38
6.5"*--->*33
4x10*--->*31
5x7*--->*28
5.25"*--->*22
4"*--->*13
3.5"*--->*10
2"*--->*3
That said, I’d go with the largest you can get in the OEM opening or if the 6x9 component you like is not available, use a 6x9 to 6.5” adapter which are pretty inexpensive and increase your options 10 fold. No need to go bigger if you are going to use a sub to cover the 20-to 80Hz frequencies, any good 6x9 or 6.5" play well in that arena. You'le likely not see much of a difference if you are going to cross them over at above 50-60 hz anyway (respective of their brand) so find a brand and model that you like, With a budget of $5-$800, better go listen and decide. IMHO, when you get into the upper end of those brands, they tend to show ther brand colors, what set’s them apart, their “signature” sound if you will. Go listen, and get the ones you like, too much money at stake to guess. Can’t say that I’ve ever disliked a $600 dollar pair of car speakers, but I can say that there are some that I like a whole lot more than others.
Diameter of speaker*|*Cone area of speaker in square inches
18"*--->*254
15"*--->*192
13.5"*--->*143
12"*--->*113
11"*--->*95
10"*--->*79
8"*--->*50
6x9*--->*42
6x8*--->*38
6.5"*--->*33
4x10*--->*31
5x7*--->*28
5.25"*--->*22
4"*--->*13
3.5"*--->*10
2"*--->*3
That said, I’d go with the largest you can get in the OEM opening or if the 6x9 component you like is not available, use a 6x9 to 6.5” adapter which are pretty inexpensive and increase your options 10 fold. No need to go bigger if you are going to use a sub to cover the 20-to 80Hz frequencies, any good 6x9 or 6.5" play well in that arena. You'le likely not see much of a difference if you are going to cross them over at above 50-60 hz anyway (respective of their brand) so find a brand and model that you like, With a budget of $5-$800, better go listen and decide. IMHO, when you get into the upper end of those brands, they tend to show ther brand colors, what set’s them apart, their “signature” sound if you will. Go listen, and get the ones you like, too much money at stake to guess. Can’t say that I’ve ever disliked a $600 dollar pair of car speakers, but I can say that there are some that I like a whole lot more than others.
