I would ditch the 20 and go with either a 20 long or 40 breeder (Petco $1 per gallon sale is on now in my neck of the woods) if it will fit in your stand.
The height of the 20 high will get annoying quickly and the size will limit your equipment choices.
For example, I used an older 55 (21 inches high) as a sump/fuge and had to build a stand to fit it under my tank, am already sick of the contortions to reach inside of it and wish I had more space for a bigger fuge section and the things only been running for 3 months.