You can find the PAR data for the current finnex on the finnex website
The problem with a tall tank is that the PAR at the substrate is significantly less than at the top.
Basically the taller plants get too much light and carpeting is hard.
You only can run the finnex at MAX in a tall tank.
There is par data for the Beamsworks on the plantedtank.net forum.
And shading is a real issue as well. So maybe consider a wider light?
Also if your tank is just really big you may need more than one light to get good coverage.