While listening to the first clip of Dire Straits, I was thinking “This sounds great! Oh no I wonder what he’s going to say.” I was relieved to hear you say the same.
I do not hear distortion, or sibilance. The Beastie Boys album (I have an original pressing) has a lot of sizzle, I think that’s just how it was recorded (or pressed) - it is one of the most noticeable in my collection.
Sibilance isn’t snappy S sounds, it’s more of a “CH” sound. Snappy, within reason, is ideal I believe.
I think you’ve got at the very least a passable alignment, probably more than sufficient at this stage with an elliptical stylus. And I think the stylus is fine. I think your turntable is fine. What you are hearing probably comes down to the entire system being overly bright. This could be due to the Ortofon, or your speakers, or preamp, or a combination of all of them interacting with each other.
At the same time, this isn’t the highest tier of vinyl audio reproduction, of course. I don’t know much about Ortofon’s frequency response, but you may find relief in upgrading to a 2M Blue (nude elliptical) stylus. Or perhaps another manufacturer with a different sound would benefit you. I always recommend Shure, and in fact there is a used vintage M97HE in box for $100 on eBay. It’s a bit of a dice roll with a used stylus, but there are plenty of replacements available, and this will undoubtedly be a different sound. In addition the more advanced HE stylus tip is able to resolve greater detail in the inner grooves where it matters most.
I think it is safe to say that the original topic of this thread can be retired: neither the Fluance or AT - a new TT plugged into your same system with the same cartridge and stylus will not make a meaningful impact on sound in my opinion.