Deep sand beds need a pretty big footprint to really be effective IME, so unless your sump is massive or the space dedicated to the DSB is fairly large you might want to pass on it altogether. I'm not really sure if putting the Diamond Goby down there would be such a wise choice either. If the micro fauna play any sort of role in keeping a DSB healthy then putting something that preys on them in the same tank probably not the best idea.
125 gal long
55 gal sump
How big is your DT btw?