If you really want to make an efficient filter, I recommend looking into getting a cheap 55 gal tank to use as a sump and then drilling the 125 for overflows. I drilled my 220 and could be happier with how it came out. It takes longer to setup, but makes for much easier maintenance from then on.
If you really don’t want to use a sump, then you can go with two SunSun 304B filters, and then add a third later, if needed.