I think the references you've seen recommending against star fish for a DSB are referring to "Sand Sifting" star fish, not brittles... Sand sifting star fish will clean your sand bed, much as chlorine bleach would clean it... It sterilizes the sand bed, eating all life out of it...
Brittle stars (Except the green ones! Avoid the green ones, they can become predatory!) I've found to be excellent scavengers.
Cucumbers I also personally recommend for a DSB, but I'd wait until the sand bed has been running for at least 6 months, if not longer, so that it's mature enough to feed the cuke. Another note on cukes, in reference to the infamous fear of "Cuke Nuke", I think it's overblown, but as a rule of thumb, if a cucumber is pretty, don't buy it. You want the ones that look like something that should be flushed down the toilet, if you get my meaning. If they're pretty, it's because they're advertising "Don't eat me! I'm poisonous!" where as if they look like dung, they're trying to hide, and are most likely not poisonous, or at least not as poisonous...
