Sump for a 75gal

[dmbnj]

I currently have an eshopps WD-150 CS wet/dry filter in my tank stand. It's small (24x12x16) with a water level of 8" which is about 10gal of water. I'd like to take advantage of the petco $1/gal tank sale and get a 29gal for my sump and redesign it with a refugium. Does this sound reasonable or is it just a waste of time?