change from wilson benesch p3.0 to magico s5 mk1

I think the Magico is a better loudspeaker but it really is a sideways move and I do not think you are going to get much better bass. In a room your size neither speaker is going to do much of anything below 40 Hz maybe even higher. If you want bass you would be better off keeping the WBs and adding subwoofers. You are digital all the way so, the first thing I would do is get a digital processor like a DEQX, MiniDSP, Trinnov or Anthem ( I like the Trinnov best) These units have bass management built in so adding subs and getting them integrated is a breeze. In a room that size I would use minimum of four 12" subwoofers. To give you "live" impact at reasonable volumes you want to boost the low end so it rises from 100 Hz and is up 5-6 dB at 20 Hz. These units also have room control so you can get the frequency response of the bass right on at the listening position. Everywhere else depends on room acoustics. 

thanks. atm i have 2 seismic 110 but dont use them for stereo just movies the vitus has 2 xlr L and R i could use for subs. is that where they go in the chain?

Agree with Mijostyn. WBs are not bass heavy speakers to start with and are very linear. Magico is similar. I would use the Seismic’s for music at least but more/bigger subs would be better. That will give you the increased bass you are looking for.