Hi, your Castle Severn 2 are audiophile speakers for hi guality amp and source into small to mid room around 20 m². It is not speaker designed for home theater or for big bass. As for hifi, it deserves realy good amp, even small tube integrated like Copland 405 or Audiomat Arpege is not wasting of money here. For home cinema, big bass I recommend to look elsewhere. Combo with one or two subwoofers (one per chanell) will also work. I use my system with two active Velodyne SPL subs with my main speakers for some 22-23 years. No problem with them. My first speaker/subwoofer combo was with Leedh Flirt speakers. Leedh have some similarities with your Castle speakers. Castle are more musical, Leedh an absolute acoustic microscope...but worked very good with class A tube amps and two Velodyne subs for bass. I have used active crossovers some 20 years ago😂. And my source was mainly turntable Rega and CEC CD player.