When one gets fairly proficient at marimba, what are some easy peices that are written for a five octave marimba?

If you're fortunate enough to have access to a 5.0 you should choose a piece and really go for it. Look into Keiko Abe stuff

i dont think there is any "easy" stuff for 5-octave marimba. the easiest thing i can think of by abe is "memories of the seashore". even though i havent had any experience with this piece, im pretty sure it still isnt a peice of cake, because keiko abe wrote it, and none of her stuff is considered "easy".