Strictly speaking,

Hard to say you dont have much info to work off of. What model JL subs do you have? how much power? What new subs are you looking at? how much power for them?

You should see a big increase in output just going to ported. Going to 15's will also have drastically more cone area so will also make it louder. More power would also get louder. The quality of sound will all depend on the subs you choose and the how well the box is designed. Lower and boomier are also going to determined by the subs and enclosure.

It will be night and day difference. The JL sub is a meh middle of the road entry level sub, the SA Z series is a whole other level.

That sub needs to be in a ported enclosure. You will need to do electrical upgrades going that big so make sure you plan for it.

Two JL Audio 10W3v3-4 10" and JX1000/1D.

I don't know.... As far as new subs, I can start with Z-12 V.3 D2 - Sundown Audio 12" 1500 Watt RMS Dual 2-Ohm Z3 Series, and go up from there.

I can also go ported...

Click to expand...

How did you go from 15's to the Zv3?

How much space do you want to give up? What is your goal? W3 and Sundown anything are completely different things for different applications.