My Valve Index works fine for me (both native and Proton), as long as I keep SteamVR on the linux_v1.14 branch. It does have some issues keeping up sometimes, but that's probably mostly my ancient GPU (AMD RX480).
From the 480 there was the 580, Vega 56/64/VII, RX 5700 and now the 6800.
From a few random benchmark site checks online the 6800 is over three times faster than a 480.
Admittedly, to actually buy a 6800 series it is probably at least three times the price of a new 480.