I have installed the DSP Audxeon D1680 a months plus and I learned and did the tuning myself.
On my Flagship, just by adding DSP only, it is definite much better that it can help to boost the bass and mid bass; or getting crisp on mid to high freq range.

The original speakers are not bad, only lack of bass and some mid bass range, will DSP can set to have more bass or crisp in the front or rear speak.
I'm still learning to tune, increase bass may come a bit of sacrifices on high frequency range or vice versa if your want more crisp sound at high freq. However with the DSP, you can also tune front speakers more crisp and rear more bass and mid bass.

However, a week ago I got myself an active subwoofer too and I would say it is amazing sound now. It make my tuning much more easier and flexible.
-Front speakers focus of mid and high freq, filtered low freq.
-Rear speakers filtered a little on the low freq and may it covered from mid bass freq range upto high freq and boost on high freq range.
-Active subwoofer, didn't do any change, flat signal direct from DSP to active sub. Only adjust gain and added little bass boost from active sub. itself.

Measuring with pink noise, I can now easily tune to audiophile profile (flat across the freq. range and slight higher of high freq range) with the original speaker + active subwoofer comparing to without active subwoofer.

Again I'm a noob on this and still learning here, however if you are using the same DSP, I'm gladly to share my setting profile with you.