Hah, how funny, I was just talking about the R8 with a friend of mine and I mentioned that the Jazz Brush card was the best one! You are right. It's amazing for Jazzy D'n'B type stuff, ala Roni Size. The Electronic (808) card is good but does not really exploit the R8's ability to sound like a drummer playing a kit rather than a sequencer playing a sample.
I paid more for the Jazz Brush card than the R8, go figure