Disclaimer: I have no experience actually running aMule on a machine with so little RAM. I might be completely wrong with my information.
I believe the speed while downloading should be acceptable. The problem is too little memory, so that it would be swapping constantly.
But: When it is hashing, it will take a very long time and your router will probably appear frozen during this time.
There are people running amuled on a nslu2 (32MB RAM + Swap, I believe) and
freddy77 contributed patches to the current developmental version to reduce memory usage - I believe his target machine had 64MB without swap.