Yeah, why not.When I go out listening, should I ask to hear the samples in mono?
I wouldn't recommend that. In your 1st posting you made quite clear what kind of sound you prefer. Just use your own recordings (preferably on CD, not vinyl) you know well, and try to find speakers where your recordings sound good.Is there such a thing as a purpose-designed listening track? Like...first you hear bass thumping and you listen for precision, then you hear vocals and you listen for realism, then you hear guitars and you listen for bite, then you hear violins at the high notes...you hear cymbals and listen for a long decay...or something else that achieves those intents.
In the price range you're shopping there are not that many neutral speakers, and quite a bunch tested so far suffer from too much brightness which is the opposite of what you prefer. Even a neutral speaker may reveal too much shortcomings in your recordings and then it may make sense to not buy a neutral speaker but one which is more forgiving. OTOH you may be able to use the tone controls of the Kenwood to conteract a bright sounding speaker.
And I also recommend to keep the TT and the Kenwood. A better TT may be very expensive, and if the Kenwood was good (loud) enough for FM it's good enough for all sources.
Of course, since I'm on the active path I would recommend active speakers like the JBL 308 measured here. I just cannot recommend a matching preamp to use as volume control. Maybe the Headphone output of the Kenwood could be used to feed the JBLs - I've done this before using a special made cable or adapter cable.