If you are putting Geos with a larger or more aggressive fish, go with larger, more aggressive Geos. G. altifrons fit the bill. Most LFS will carry them as "G. surinamensis." They are one of the most common geos out there. I see them at places like Pet Supermarket all the time. A lot of mom and pop stores can get them (they are usually on lists from the big distributors like Segrest Farms) but you may have to ask them specifically to bring them in. A group of six would be good.
The one problem I see is that a group of fish that have the potential to grow 10"+ and aggressive may be cramped in a 125 with tankmates. Orange heads are beautiful but they are also on the smaller side (8" max with extremely ideal conditions, but more like 4 - 6") and fairly placid. I've never had dats, but if they're aggressive they may push the orange heads around.
I've kept several species now including G. winemilleri and G. brachybranchus, which both grow pretty large, and they really only sift maybe the top 1/2" - 1" of sand, max. If you're just looking for something to sift out uneaten food and keep algae from growing on the top layer of sand then they're probably fine. If you're expecting them to eat detritus or sift a deep sand bed to prevent things like gas pockets from forming, no species that I know of really fits that bill. I still have to do that manually with a long-handled algae brush or piece of PVC.