I have a 68030 @ 40mhz for my Amiga 500 and it is pretty quick. I wish Jens could build (as some others have stated) something similar to the Viper 530. It would be nice to have 128mb onboard so as to be able to use Netsurf (although it would probably crawl).
I suppose a 68040/060 board would be totally out of the question

I know the cost would outweigh the benefit, but it is nice to dream once in a while.
--- I am ok with an 020 board... but would it be possible to increase the memory? I could see myself building another Amiga 500 system with Jens new accelerator.