They are not very efficient so they'll require a bit more power than you'd expect. I'd recommend at least 60 watts per channel. More is even better.
Looks like the OP is another seagull member here on AK, they Drop in , ask a question and fly away never to be seen again . but for anyone else who might have a similar concern or question about CSW speakers.... The ensembles are a solid candidate for Bi-Amplification , in fact they excel in that configuration far better than speakers that simply have dual binding posts. even pairs of "budget" ( relative to Krell, Pass labs etc) amplifiers in pairs are a good match. NAD 2200 PE, Adcom 545 II, 555, Carver A500x, Acurus A150, as well as lower end models from B&K , Parasound , Rotel etc..
You can certainly start with a single, but the Ensemble and Ensemble II are prime for a second amp to exclusively drive their bass modules ( note I did NOT use the term "subwoofer",
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I highly recommend the satellites made of MDF and NOT the ABS (plastic) version. Can you use a powered subwoofer with a 4 piece or 3 piece ensemble system. absolutely. can you use bigger more powerful amps to drive them Certainly. The ensemble system is a great system to experiment with. low frequency performance changes with positioning, separating the bass units may even out the low end in a room, stacking them near a wall will allow for acoustic coupling to increase the bass performance.
Market values are fairly low for Ensembles but that doesn't mean they aren't a high level performer. Kloss was able to coax some solid performance out of his design and component choices and I've found that amplification makes all the difference in their performance overall.
