I have a 2015 Kona Explosif frame that is about to be replaced. It’s light, zippy and sparkly purple! It’s on the lighter side of the All Mountain spectrum but I’ve been happily riding it with a 160mm Pike. I run it as a single speed but gears can be added if you so choose. I have 2.6 Noby Nicks on it now but it’s tight so a skinnier 2.6 like a Specialized or a 2.5 would be a better bet. I could do it for something like $450 with freight so it stays under your $50o budget (decent headset included). Paint is custom and in good nick. However it has a few scuffs, as a mountain bike should, but looks great.
Please excuse the uncut break lines!
Sorry, it’s a crap pic, I’ll send you some better ones if you’re interested.
An older but better photo: