This was the torso angle that Dorian Yates liked to use for his curl-grip rows, but I've found that rows done in the Smith machine hit the upper back a little better than barbell rows. They really allow you to contract the upper back hard.
The Smith machine automatically keeps the bar in a very efficient path, so there's no energy wasted in trying to keep the bar close to you like with the barbell row. You can focus on the execution more intensely. Do 3 sets of 8-10 reps.
If your size and strength gains have stalled out, it's because you made things too complex. It's time to get back to basics and get strong... using only 4 reps.
Starting with a weight you can curl 12-15 times, do 8-10 reps on steep side of preacher bench, match those reps on the angled side, then stand and rep out.