Couple of things,
There is nothing wrong per se with a HOB overflow - had one set up on a 150 for about 10 years, and the only issues with it losing prime were totally user error, and that was only twice. Nice way to try out a sump without spending the money on a drilled tank.
That said, I've moved on to built in overflows on my two larger tanks. As far as I know, all the major manufacturers offer reef-ready tanks, certainly Marineland and Aqueon do.
The only downside of the HOB's may be that they only pull from the surface, but that is fairly easy to overcome with either creative returns, or circulation pumps.
The idea of 3 layers of poret foam in the sump is solid, and the simple approach is wise idea also as it avoids a lot of engineering errors. DAMHIKT.
180g - Tropheus Bemba, Syno Petricola
125g - Planted SA Community, Firemouths & Acaras
90g - High Tech Planted
20g - low tech planted
6g - Eheim low tech nano planted