The output caps are a large value. I agree with Mcandmar, another electrolytic won't get you where you should be.
What you are looking for is a film cap. Daytons are inexpensive for that value and voltage rating. They will make an appreciable difference in the sound.
Do a search and read this thread, you will find a pretty good list of film caps available that will make an appreciable difference. (I don't have a Crack, so haven't done this myself)