I originally started out thinking that I would be happy with Euclidian patterns for Drum sequencing but I quickly found I wanted more control so added a Roboux LL8 and later a Beatstep Pro. Is this someting you've thought of or are you completely happy as you are as you already have a lot of trigger options?
Enjoy your spare HP, don't rush to fill every last space, this is not like filling sticker books. Resist the urge to 'complete' your rack, its never complete so just relax.