And after all that, you'd still have a 68020 under the hood. You could, of course, spend an eye-watering amount of money on a 68040 accelerator... and then... you're still not going to beat the DX2/66. (Let's not even talk about the performance of AGA versus a local bus SVGA card)
It feels like I've heard so many Amiga users say that they finally broke down and jumped ship when Doom and the DX2/66 dropped. It really was a gamechanger. Before then it was possible to argue that a '040 Amiga 4000 still held its own against a DX/33 or maybe even a DX/50, but not this.
There were a lot of things that came together to kill the Amiga, mostly Commodore's mismanagement, mismarketing and complacency, but as the final blow to it being a viable computer with a future in the eyes of consumers, I feel like the DX2/66 was it. It would have killed the Mac too if Apple hadn't woken up to smell the coffee a few years prior and had Power Macs ready to go.