It really depends on the system components. 25 W is generally plenty for a small room. I have a 250 W Hegel amp (into 4 ohms, 150 W into 8) on my main system in a large open room and it makes my 4 ohm DALI Rubicon 6 sing like nothing I've heard before. I tried those speakers with a 60 W Yamaha before I bought the Hegel H190 and it just didn't sound right. The Yamaha is GREAT with smaller or less demanding speakers like the Zensor 1 they're powering now in a large bedroom. I also have a 45 W Parasound amp powering some KEF Q100s in a small bedroom and that's more than enough power, sounds great. Some speakers just need more current than others.