Need advice: Buying a friend's HD 660S2 + Fiio K7 bundle for $500, or should I go for ATH-R70xa or ZiiGaat Horizon?

Hi everyone need help,

I’m looking for some advice on my next audio setup. A friend of mine is offering to sell me his used Sennheiser HD 660S2 + Fiio K7 bundle for around $500 USD. Do you think this is a good deal?

For context, another friend recommended that I buy a brand-new Audio-Technica ATH-R70xa paired with a Topping DX5 Lite/II instead.

Or the ZiiGaat Horizon, especially since I already own the BGVP T01 Pro.

Which of these paths would you guys recommend? I'd love to hear your thoughts on the value of my friend's bundle versus the other setups. Thanks in advance!