Whether you think there are players of equal caliber out there, the point I was making is that he's attracting a lot of attention and players like that generally do so because big clubs see that they are world class or have the potential to be something special. We won't be getting Stones this summer and that is for certain, I also doubt we'll get anyone at the same level. Top class defenders would be very tough to prise away from big clubs and those at smaller clubs would be wise to wait before moving here.
Koulibaly has been mooted for Everton as a Stones replacement, he's a good player but already 24 and I, personally, don't think he'd be a huge leap over what we already have. Mustafi looks good (and was already at Everton wasn't he? There's some weird Everton link going on here) but there'll likely be competition for his signature if he leaves, and I don't think he'll hit the same heights as Stones although maybe I'll be proven wrong over time.
We could also go for Dragovic, but my point was that most of these are unknown quatities, the premier league is not the same as other leagues and there are no guarantees but Stones is already premier league proven and he's already looking like a future Terry or Rio level England player, the biggest clubs in the country (and some from elsewhere) will be going all out to get him, so we should look elsewhere as I don't imagine he'll want to join Louis Van Gaal's Europe-free army next year, sadly.