KTM offers three different wheel / hub combos on the 640. One of them will work on the 525 (I am trying to sort that out now for the 525 I will pick up in 2 weeks). Three measurements must be correct: overall width, sprocket alignment and rotor alignment. So far I have the last two but not the overall width.
My 450 EXC as a dual sport was not blown all over the highway, could cruise comfortably at 65 and excelled off road. It also had almost no vibration. With the EE soft seat it was as comfy for me on the road as my 625 SXC but it had far, far less vibration.
Maintenance on the 450 was minimal. No valve problems surfaced in all the years and miles. It was as reliable as any street bike but a whole lot more fun.
I had a 950, but being a smaller and lighter guy it was just too tall (a wide seat) and the weight was too high (once it started to tip over I went). The 450 was a joy after that. (The 950 did everything the 450 did and I took it places that I should have been on the 450, not the 950, but the 950 always came through.)
Pro Moto makes a billet alloy luggage rack for the new 525 subframe. They say you can carry quite a bit with it unless you are hammering the whoops in which case they say you should not carry more than 15 lbs.
When I get the 525 I will post more info on how it works as a dual sport with the emphasis on off road, which is what I want.