I meant like something you can buy off the shelf that can run [shader or whatever] code on the GPU, loaded with OpenGL - there might be something like that for PCI, I guess; dunno what is available. Offload the CPU. Now we're talking about an upgrade!! (At least potential upgrade, as with all things it needs software/OS support.)
I guess the accelerator would have to be close to 68040@25 performance for it to sell well - 'run > OS3.1 well' - even though I'm not into that, a large part of the target audience could be.
Ethernet/USB: well I didn't check availability. That's not it then, unless there are some extra features/new slant.