Hey ricone! Welcome...
I own the X5s; all X series are voiced very similarly. As Tyson points out, if your room is larger, the X3s will do better given their larger woofer. Both the X3 and X5 have powered subs, leaving an easy load for an amp to drive just the Bayma AMT and midrange driver. They sound equally excellent with small tube amps to high-powered D Class Amps such as Cherry. One aspect of this design I appreciate is the ability to control (albeit manually) the sub's response. I find with some recordings the bass response is either lacking or over-emphasized, having that ability to fine-tune that to my taste is a nice feature though I don't do that often.
Not knowing the size of your room, I think the X4 would probably be the best choice, given you have already invested in an end-state amp with lots of headroom. I rolled a lot of amps until I found the one that checked all the boxes for me (LTA Z40i+). Your D'Agostino/DCS combo would be next level with the X4s. I heard the X4s at the Capital Audio Fest earlier this year and was very impressed. I understand that Clayton has made further refinements with the crossover since that show, which elevates the sound that much more.
The good news is you really can't miss with any of these amazing speakers. Again, welcome to the site and best of luck on your journey. Please keep us updated! John