Problem with the Amiga is all the custom hardware needed to be emulated, and still have enough CPU power to emulate the drives, input devices (Mouse/Joy/Clock).
Some things the GP32 has going for it that would be good for Amiga emulation...
8 megs of RAM.
GP32 RAM is 32-bit, where chip ram was 24 bit on the Amiga and fast ram was 16-bit
SMC-loaded .ADF files would still be faster than real Amiga floppies
Chatboard for possible keyboard emulation
320x240 is fine for most NTSC games.
Two speakers for stereo sound
The LCD screen of the GP32 can handle as many colors as the Stock A500 could.
If the DC port runs at about 200MHz at like %60, I'm guessing with 160 to 166 MHz, it would be like %40 of the speed of a real A500. If that... But it'd be a good start for optimizing.