If you think your Amiga's slow, like when you're ray-tracing, then what you
need is the A5000. At £295, some people could say it's expensive but compared
to others, the A5000 is quite reasonable.
Actually fitting the card, in theory, is pretty simple. You unscrew your Amiga
after turning it upside down, then take out the 68000 chip, put it into the
slot on the card and then fit the card into the empty space where the 68000 
was.
2 plastic lugs are supplied that stick into the Amiga for the card to rest on.
This was easy, but when I turned my Amiga upside down again, to put the screws
in, the card fell out. So I put the Amiga on a small round table and by lying
on the floor underneath it, put the screws back in.
Once in position, back on my desk, it was perfect !
The card uses a 32-bit processor which is the 68020. Okay it may not be a 68030
but it's good and as mentioned before, for the price, is reasonable.
It comes with 1 meg of 32-bit memory and can be expanded with another 4 meg of
32-bit memory.