HD 600, or a new amp?

[BLCT]

I found an add posting for a HD 600 on Kijiji, the guy claims that it is in mint condition and he only worn them a few times. As I question why hes trying to get rid of them, he says "I'm just looking to sell them". He's selling them for $350 CAD (about $267 USD), but I talked him down to $325 ($232). Is this a good deal? And if so, How do I go about verifying that it isn't a counterfeit. I asked him if he has the original receipt he said no. He does however have the original box and wires.

In the other hand, I was thinking of getting my first tube Amp for about the same price. I haven't decided on what amp yet, but something around that price range. My setup consists of a HD 650 plugged into an Schiit Audio Mangi 3, and Modi 2.

Now there's rumors floating around about the HD 600 family are getting replaced with a newer headphone/newer line. I've never owned a HD 600, but listening sessions with my friend make it not as bassy as my HD 650. However the clarity is much more present, especially on the trebles and vocals. I've only had about an hour to sit down with them. As my friend (who owns a pair) lives in Calgary, and I live in Toronto. So my experience with them aren't the best case scenario. Now, do you guys think that the HD 600 and HD 650 are too similar sounding, that dropping $300 ($220 USD) on them would be pointless? Or should I pass on the offer and just buy a new tube amp. I have attach his pictures that in posted on that ad here. So, What do you think? Are they fakes?

Also I'm open for recommendations for tube amps! 

Edited December 30, 2018 by BLCT
Added pictures