Sub woofer help seal or open?

Hello ,
I need suggestions from here , currently I using 3way seal speaker ,off course not happy with low frequency.
So , I decided to add 15in woofer for my 3way seal speaker. In case which one is right choice for my existing system?
For seal AE 15 TDH or AE dipole 2x15in per side .
For future I would like to add full range driver and can be used at two ways speaker too that is why I consider to use open baffle .