A proper stereo setup also has separate left and right channels ;) I don't even sit at the centre of my two DLS M66s, and I can hear the whole stereo soundstage.
I like that this Headphone Edition is also a high-quality pre-amp. Just buy some good amplification and you're ready for "proper" stereo.
5k for that Naim, you mean? It's not even 4k here. Not saying it's an inexpensive piece of kit, but I fully support blowing that kind of money on hi-fi if you like good sound ;)
About $350, but that was a very good price I gave someone from another forum I manage, and only because I found out that those ACA ports on PS5 and such are perfectly fine for me. According to sold items on eBay, the price differs quite a lot, depending on condition.