Power for speakers, too little will damage a speak

I have recently purchased a Fisher 500B tube receiver, I am driving a pair of Mirage M1si speakers with this receiver, It is rated at 30 wpc into 8 Ohms, it has had no mods except I have insatlled 4 New 7591 electro Harminex Power output tubes, It sounds realy good, But I want to know if I am doing any damage to my speakers? With his low a wattage, I normaly , I'm ashamed to say usea Krell fpb 600.any opinions please. Thanks Alan.
If the volume you are attaining with the combo is satisfying, and you're not hearing any high freq. distortion(clipping): You are not going to hurt your speakers. Clipping burns tweeters, and sounds really obnoxious. Tubes do it more softly than SS devices when driven hard, but- You will still hear it when it happens.
The standard explanation for how too low a powered amp can damage a speaker goes like this -- a low watt amp coupled with an inefficient speaker will make the listener turn up the volume which will then push the amplifier into steady clipping. The clipped amplifier output waveform now contains large amounts of very high frequency distortion that is being feed into the speaker. It is this steady stream of high frequency content that is normally never found in music that can burn out a tweeter.

Your tube amp won't clip in the same manner as a solid state amp, but it will still clip. Whether it actually damages the speaker depends upon how long the clipping occurs, the robustness of the tweeter design and the overall design of the crossover network. My guess is that it shouldn't be a major concern.

You do realize that you're the only person in recorded history to have every paired these two components?
M1's are great but really need 200+ watts to sing.
I doubt that the distortion from the amp can hurt the speakers. However, I'd worry about overdriving the amp. Pushing it at max will shorten the life of some very hard to get tubes!
Thank all of you for your comments, I have not heard any clipping going on, and yes I do know what that sounds like.
To me it is amuch smoooother sound, with I must admit pretty good detail, I would have never believed a 30 watt 50 year old receiver could sound this good, but it does.
I only have to turn up the volums to about 11 oclock to enjoy the music, that is through the phono satge of the receiver, yes it is nice, now I owuldl like to have some upgardes done, capacitors replaced, etc.
If you don't have hum/hiss problems, leave the caps alone. New binding posts and rca jacks and power cord will help.