The problem I see with using both a DSB and a trickle filter( wet/dry) is that while the W/D is efficient at reducing ammonous nitrogen compouunds to nitrate, because of the time lage and distance involved you will have some available N in the water column. In either a LR/DSB or LR/plenumn the theory is that the nitrite reduction takes place at the surfaces due to aerobic bacteria and the nitrate produced is reduced to free Nitrogen and the odd carbon,etc molecule released or consumed by the anerobic bacteria in the deeper layers of the DSB or the interior of the LR. It's the proximaty of the 2 zones, coupled with osmotic , hydraulic factors, depending on water flow and other factors, that makes or breaks the system.
My fear is that with a 50 gal tank and a fractional volume sump, you just don't have enough space and volume to exercize a lot of options. I suspect that a large system such as Mikes with its sheer tank volume, coupled with mega water movement and sumps, refugiums, and a super skimmer has more chance of success, if for no other reason than sheer volume, plus the large display tank to biofiltration ratio.
Its hard to simplify this without creating more questions than answered, but the bottom line is you are trying to replicate the ocean in a drop of water, so to speak. I think the bigger the reservoir, the more grace you get.