Yep, it would suck HP very fast. I'm going to end up with more Mixers and Stereo Mixers taking up HP in my racks than I'd like, I'm already taking up 62HP for Mixing in my cases and I still need/want more!
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.