Is there any truth to this question?

I was surprised at all the viewpoints this thread has generated. From a fact based scenario I'm am sitting close 1.5m from speaker, not ideal. I listen for the most part at 85-90 db maximum so at best I'm using 4 watts with my Vandersteens, correct? The 50W should give me 101 db to play with, way louder than I've ever listened to music at home. Could I reach the clipping point playing small group jazz? I like the YBA sound but can't afford there better amps besides a YBA 1 is only 85 W with more current. I guess I'll never know so I guess the best thing is to forget the audiophile rules and just enjoy the music.

Seems like you have a pretty darn good setup as is! As you say, enjoy the music.

Power is most likely not an issue with your nearfield listening position.

Devils in the details.....

86 db speakers are not very efficient. you may need more power to drive them vs more efficient speakers. So, to me, this conversation depends on the interaction between your amp/speaker cables and the speakers. That YBA amp may be absolutely wonderful matched with your cables and speakers. on the other hand, I don't know what db efficient speakers the amp manufacturer recommend that you pair with the amp. 86 db is on the ragged edge of making amps work too hard and therefore you may need proper power handling capability (i.e. huge power supply capacity) in order to drive less efficient speakers). All that said, turn it on, listen. Does it sound like the amp is working too hard? sometimes biamping with the same amp will fix this. other times, well, either more efficient speakers or better more powerful amp is required. If you are really concerned about this for your own system and not just an intellectual conversation, then go "borrow" a few more powerful, nice, clean amps within your price range, in-home test them with your favorite music at the listening level you are used to, and tell for yourself. A good stereo store will let you take home and audition. If they won't (even after taking your credit card information), then they aren't worth my time. I won't buy blind. Or, find a good friend and borrow their amps for a quick listen. or have a wine, dinner party with friends and have them bring their amps over for a in-home listening session. There are several fun ways to do this without buying first. But, 86 db speakers are not efficient. Far from it and they are difficult to drive. However, a class A Pass, Threshold, Mark Levinson (20.6, 23.5, etc.)amp at 50 wpc or more would not have a problem at all driving these speakers. I like the sound of YBA equipment (if you can find it), but I don't know about their load driving capabilities.

enjoy

I have never heard a high powered amp of any sort that was capable of delivering great dynamic contrast at low volumes, detail without an artificial edge, and a truly enveloping soundstage like a very low powered SET amp (10, 45, 2a3 and 300b). But, these kinds of amps have quite limited applications. Where a little more power is needed (anything well over 10 watts) I would look next to an OTL. These amps can deliver most of what a SET can deliver, and in a very critical area (dynamics, liveliness) they are pretty much unmatched. There are some matching issues as well with OTLs, so I cannot say whether any particular one would work well with your Vandersteens. I would certainly give something like the 30 watt Atmasphere a trial.

This is a rough generalization, but, for me, the least appealing kind of amp is a high-powered tube amp with oodles of pentode or tetrode tubes in pushpull operation. A lot of these sound hard and artificially edgy.

I find that many of the better, high powered solid state amps no longer sound particularly grainy, and while none have quite the natural attack (leading edge of the note) of a SET, they are not nearly as edgy as they once were. What I find is that they sound somehow dull, flat and uninvolving unless the volume is cranked up a bit. I've heard some systems (not my own) with certain high-powered solid state amps that sounded reasonably good, but these amps were extremely expensive (Soulution, MBL, and D'Agostino).

I have heard, and liked, some lower powered solid state amps. I think the lower powered Ayre amps sound reasonably good. I particularly liked the First Watt J2 that I had in my system for a week (borrowed from a friend). This 25 watt amp was quite natural sounding once it warmed up. I would not trade in my SET amp for the J2, but, then again, the J2 costs less than one tenth of my SET amp. I would bet that its 25 watts would be enough for the Vandersteens at anything but extremely high volume.

If you want to test whether an amp can deliver enough juice for demanding situations, my suggestion is to find large scale choral works. For some reason, systems will distort (voices become muddled and fuzzy) at what subjectively does not seem to be that extreme a volume level with such works (look for something like Rachmaninov's "Vespers").