The bass and drums board is cheaper, but all in all the DR-770 sounds much tighter and more full in my opinion, plus you have independent effects to use on the dr-770 that you can use to become even more expressive. You can get it from musicians friend for $379 and from zzsounds for $349. See if a local dealer has it so you can compare the bass and drums xpansion to the dr 770. you'll see what I mean.