Your best bet is the Razer Blade Stealth, for 1,399.99. It is considered the best lightweight gaming laptop. If you want to really squeeze in the whole entire budget, you might want a Razer Blade Pro for 1,799.99 for the extra punch.
The only 8 core laptop i could find was a Asus ROG GL702ZC, but it's not very sleek. Uses Radeon 580 i think. Otherwise, you can use the Xiaomi and replace the cpu if possible.
I can't find any 8 cores, but I found a 6 core laptop. Not as sleek as Xiaomi, but still similar. It has gaming, but I could not find anything else sleek as it.
Alienware 17 laptop, $1,500. What are you planning for 4+ cores?