Looking for speaker recommendations that I can purchase on Amazon.com

@willemj thanks for your reply. Given that I don't need the extra power of the P5000S, is there any advantage to the P3500S? For a couple more weeks, I can still return the one I have and get the P3500S if that would be advantageous. However, I assume from your message that there is no reason to do this.

Also, is there any reason to consider the newer Yamaha PX3 or PX5 power amplifiers instead of the one I have?

In regard to my personal experience with this amp, here is what I wrote over in the thread where the amp was recommended to me:

I have been reading a lot of reviews and thinking about distortion, clarity, detail, sound stage, etc. To my (somewhat inexperienced) ears, this setup with the Yamaha power amp and the Polk RTi A7 speakers, lets me experience a very satisfying level of all the things I have been reading about that come with the best speakers and the best components. With my current system, the sound stage is surprisingly expansive. The detail and clarity are amazing. The harshness in the higher frequencies is gone. I am beyond happy with this amp.

I'm still shopping for speakers in the price range of $5000/pair. But now I am able to enjoy my current system without any complaints.

What you are describing are precisely the benefits of big power. As you Americans say about car engines: there is nothing that beats cubic inches. Just imagine the amount of physical energy produced by a symphony orchestra. The speakers have to reproduce that, with an efficiency of perhaps 1 % (a proper calculation is beyond me at this time of the day). Even with such by audiophile standards relatively massive amplifier power, you can only hope to reproduce such a symphony orchestra at little more than postage stamp size (a domestic room will not allow anything more anyway). As you discovered, watts fortunately do not cost that much anymore.
As for thePX3 and PX5  successors of this amp, apparently their fans do not switch off completely, so they are less suitable for domestic use.

KEF LS50s are not bright at all. In fact, I was surprised to find they're warmer than all other speakers I've had in my system. I have Spendor 2/3s (often described as "pipe and slipper" speakers) hooked up to the same Yamaha amp as the LS50s. I can do an A/B comparison with the flick of a switch. The KEFs are no brighter than the Spendors. They're actually a tad warmer.
 

A pair of KEF LS50 sound exceptional for their price.   Quality stands are required for their proper performance and this additional purchase must be calculated into the purchase cost (got my KEF branded stands off Amazon as well as the extra dampening stand fill).  The LS50w self powered is another path to consider and would remove any amplifier issue (return the Yamaha).  You would have a system that would not disappoint in its musicality.  I have a set of the standard LS50 that when placed into my main system always amaze me with their performance.  

I'm passing along some info I have been gathering on these various speakers.

The TANNOY Revolution XT 8F is one of the speakers that was recommended to me here. Below are some quotes I pulled out of reviews. I was looking specifically for critical quotes regarding the higher frequencies.

The first comment below concerns me a little bit, even though most of the reviews are very positive.

https://www.whathifi.com/tannoy/revolution-xt8f/review - "Tonally, these Tannoys aren’t the sweetest sounding performers around. You’ll have to take care not to partner them with anything that sounds overly forward or harsh, because they’ll do little to tone these qualities down."

"We’re pleased with the stereo imaging. These speakers shine when placed well out into our test room and given just a touch of toe-in towards the listening position. Once the Tannoys are positioned with care their sound stage is crisp, nicely layered and pleasingly solid."
"give them a larger room to play in and the XT8Fs will shine."

https://hometheaterhifi.com/reviews/speaker/floor-standing/tannoy-revolution-xt-8f-floor-standing-sp...
"My only sonic critique of note is that the Torus tweeter’s lower treble seemed slightly less delicate and precise than my reference speakers’ ceramic-graphite tweeters. I noticed the difference primarily in the effects in “Welcome to the Machine,” panned between the side surrounds (which use the same ceramic-graphite tweeters) and the front channels. Also, cymbals sparkled but their shimmer didn’t decay quite as cleanly. While the difference was noticeable, it did not detract from the immense enjoyment the XT 8F trio brought me on every piece I played through them."
"Often, playing full-throated female vocals loudly will expose a speaker’s crossover points, as the tweeter or (more rarely) the midrange audibly compresses at the bottom of its range. With the XT 8F, there was no sign of overload no matter how hard I pushed."
"tape hiss was lightly accentuated by the Tannoy Revolution XT 8F compared to my reference speakers"
"Few if any similarly-priced speakers offer the Revolution XT 8F’s heady combination of top-notch full-scale sonic performance, attractive design, and excellent build quality. Highly recommended."

http://www.theabsolutesound.com/articles/tannoy-revolution-xt-8f-loudspeaker/?page=2
"Time and time again, the 8F was able to decisively reveal amplifier differences, a testament to its resolving powers. For the record, it gave its best imaging performance when partnered with tube amps that also happened to flesh out the most convincing spatial impression."
"The Tannoy Revolution XT 8F was Robert Harley’s top discovery at the 2015 Consumer Electronics Show. His first impression was as follows: “After listening to it and looking at the real wood enclosure, I guessed the price at $7000 to $10,000. The Revolution XT’s price was then revealed to be just $2600 per pair.”
"The Tannoy packs a virtuoso midrange that is competitive with speakers approaching $10k retail."

http://www.hifiplus.com/articles/tannoy-revolution-xt-8f-floorstanding-loudspeakers/
"I guess, when it comes down to it, I want my system to entertain, not to impress. I’d like it to do both, of course, but that tends to cost considerably bigger bucks than are being asked for here. Any loudspeaker selling at the price point of the Tannoy, or even considerably more, is going to have some defining compromises, and the temptation for many makers will be to take care not to offend."
"In some respects, the Tannoy comes across as the antithesis to something like the, broadly similarly-priced, Monitor Audio Silver 8s that I reviewed a few issues back. The MAs are very good loudspeakers that rarely put a foot far out of line. In comparison, the Tannoys are somewhat more bullish and, perhaps, a little uncouth, but they sure know how to have a good time. If the MAs are a well-trained Labrador, honest, reliable, and solid, then the Tannoys might be a Springer Spaniel, loads of energy, fun, and boundless enthusiasm, but prone to knocking over the occasional vase. Neither speaker has the monopoly on rightness, nor any fatal flaws, but you’d be unlikely to find that both will float your boat equally, and much will depend on personal taste and preference."