Piero, I have the Sigs and use a 130 wpc McIntosh MC2000 tube amp from time to time on them. If your amp has a good power supply you should be fine up to a point. When that point will happen depends on how loud you want to play them. If 130 wpc isn't enought for you, realize that 260 wpc WON'T be twice as loud. You would need 1300 wpc to double the volume. I've seen the impedance graph on the Signatures. It's pretty flat at around 4 ohms and not bouncing all over the place or dipping real low. The worst it showed was 3.3 ohms with the switch set to high. Your amp should be fine on the 4 ohm tap. Good luck.