My nickels worth ..
If greater choices means anything it could be that amps have now been the more improved. Namely by a wider selection of hybrid amps.
Preamps however make a strong argument for settling into first place too as its taking less dollars to get astride the threshold of diminishing returns with the most recent versions. Ive seen articles which allude to the facts that even some of the mid to upper tier receivers preamps come quite close to the performance levels of preamps ranging near the $2K - $4.5K arena.
But Ill vote for speakers. In spite of the fact Im finding specific very nice to great personal choices get well into the average of $10K, theres so many out there now which do a more than satisfying job for far less.
Somehow I feel each category here is ahead of the game vs. their constituents of a decade ago amps in graeter or more broad spread appeal due to design innovations. Preamps seem the ones favoring value as its chief concern. Leaving speakers determined as being improved by technology and materials, best.