30 to 50 watts seems to be all I desire

The AVERAGE watts even on inefficient speakers playing loud is only in the low single digits. Even an avreage twenty watts would either drive you out of the room or else make youd deaf. Power is used for very, very short term transients which can be 20 to 30 dB(20 Db is a multiplier of 100). These transients are very short and good amps recover from the overload very quickly. But even good amps clip these transients and weaken the fidelity. If you want the best sound as my old friend George Bischoff(Melos amps, 200 and 400 watts triode) said - a good big un will beat a good little un every time.

I have three amps, the “biggest” being rated at 6.5 watts per channel (parallel single-ended 2a3).  I bought a pushpull 349 amp from an Italian builder.  I had the amp for a couple of years and had no idea of its output capability.  When He came here for a visit, I asked him, out of curiosity, what was the output capability of the amp.  I could see that he was annoyed by such an irrelevant question; he thought for a brief moment and threw out a number—around 5.5 watts.

Listening to mainly Jazz at volumes less than 85db, normally.

I used to listen close to 90dB when I was younger(20+ to early 30s) with peaks hitting 100dB. Now a lot older, my average listening volume is 65dB. At these levels, any amp would do it.

I occasionally listen at 70 to 75dB only for a short period of say 10 to 15 minutes.

The average SPLs I recorded with the Radioshack meter (~65dB).

 Power requirements can be all over the place depending on speaker efficiency, volume, room size, and even more. To get to the point, so many years ago, I had speakers with 103db sensitivity. They were horns of course. I ran SS mono blocks rated at 90 WPC, and the meters never moved, nor should they. The bass was like I have never heard since, but midrange horn was not so good.

  My point is that there are too many variables to set yourself thinking about a certain amount of power before understanding the needs of your listening experience in the first place. 

Another component to this topic is the input/output sensitivity of preamp/amp. I had a Decware Torii Junior, 20 wpc, with a preamp, Canary C630, max gain of 9db. Couldn't get over 90db volume (at 10') with preamp wide open. Tried a Rogue Audio RP-7, with 14db gain, could not get even 70db listening volume cranked up. 

Input sensitivity of the Decware amp is set to 2 volts, most are 1 volt or less. So it takes twice the preamp signal to get to same volume. I now have a PrimaLuna Dialogue HP, with input sensitivity of 1.2 volts. Almost the opposite issue now, same Canary preamp, volume set at 2 of 10, dB listening volume is plenty, 85+. At 4, music transients are >100dB.