Searching cheapest Radeon to substitute 6 GB HD7970 Ghz Edition

[hodak]

Hmm i think the more recent RX 470 is faster, more efficient and has HEVC support than a HD 7970 GZ edition and is dirt cheap in the used market these days

[villeneuve]

Hello,
I'd like to replace my current 6 GB HD7970 Ghz Edition, which I need for another system, with a more current Radeon GPU that's fully supported by amdgpu and performance wise is at least as fast as the 6 GB HD7970 Ghz Edition. Which GPU would be the cheapest option?
Thanks very much in advance!
Greets!