Adding a sub has more benefits than just the lowest octave, they can smooth out room response and almost always make the soundstage larger as well as having some ambient cues. Also it relieves your mains of trying to reproduce the LF, leading to generally less "forced" sound.

Doesn't really matter what sub you use, so long as it's decent, the biggest issue is how you integrate the subs. In this case a DSW with Meridian gear would probably integrate well...

I used two SVS Ultra 13 Sealed box subs with my Meridian DSP6000's (which are not bass shy) and the result was far better than just the 6k's.

Roon/Tidal, SBT, Trinnov ST2 , Twin Devialet D premiers, Vivid Audio Giya G1 Spirits, dedicated and treated room.
Meridian gear: 568.2mm and DSP5000's acting as TV speakers.