The only invert that has worked well for me is the Tigar Tail Cumcumber, but it needs something to munch on and will deplete your sand bed of the natural flora and fauna. Sand sifting stars are a no no in my book unless you have a larger tank with an established sand bed, the vast majority starve in the average hobbyist tank, there are always the exceptions though, still not worth it to me.
To keep the sand clean without an invert, I make sure the flow is directional enough that detritus is not allowed to collect. I also vacuumed sections of the sand bed with each water change.