There are Aphex modules which FIT the dbx rack, but confirm voltages before you assume they will work once in the rack. I have two Aphex 9000 racks filled with dbx and Aphex modules, and as far as I can recall from when I went through it, the dbx modules want 24vdc bipolar and the Aphex modules want 15vdc bipolar. There is an Aphex power supply which supplies both voltages and one which only does the 15v. I have never tried to run the 9000 series Aphex modules in a dbx 900 rack... no idea if they would work.
I am pretty sure that there are earlier (perhaps black faced) Aphex modules that do work, and I know for a fact that BBE made 900 series modules (I owned a few).
tom