I've seen a DS US11 powerwall m/g go for 425 euros recently. Also I've seen asks for >£1500. I'm inclined to say £400 is actually a good price for a US13.
Gustodaninja - who sells loads into Oz - regularly sells the 2001 Bred DS and it never goes for much over $500
As for the atmos, you might have more luck selling them by someone like Gusto back into Japan.
Adidas, you'd have to pay someone to wear.
Depends if you want a quick and fair sale or wait it out to get more like what you want. A shoe like the powerwall is worth more in a trade at an event than what you might sell it for.