The GBA doesn't have any 3D graphics hardware, yet it renders that Tomb Raider game with 3D graphics in real time using a software rasterizer, on a CPU with half the clock rate of the CPU in the PS1 and with a fraction of the RAM of a PS1. So no, this is not "just a tiny step down from a PSX".
The N64 can barely run Quake for PC. And SCummVM.