I have an original Abacus Super C 128. It is kind of nifty, but has a terrible manual full of typos. I dunno about recomendations as I haven't gotten too far past "hello world"
I actually wrote a paint program for 80 column bitmap mode that mixed Basic 7 with machine language calls for doing the drawing. The 80 col chip had a fast block copy function built in. could copy 1-255 sequential bytes in 1 call. I believe it was masked too...but don't quote me, it's been a while.