when i use Deadlock's Stacking Beltboxes, i also use Deadlock's Compact Loaders instead of Loader Redux. I hope that both can be powered respectively transmit power along the belt without the need to build two power poles to bridge a gap at them ...
and yes, lots of power poles cause problems: not only the number and their influence on fps/ups, but maybe even worse the builtin limits in factorio about the number of connections that a powerpole may have:
(from the very bottom of https://wiki.factorio.com/Electric_system) ... automatically connect ... according to the following rules: -1- connect to available poles starting with the closest one, -2- it won't form a 3 pole triangle, and (most importantly) -3- It will not be connected to more than 5 other poles
powering several belts in a multi-belt mainbus might easily cause all available 5 connections to be exhausted for connections to other belts and thus power poles next to those belts might be unable to connect to them ...
i have seen this problem on some other mods, eg when offering powered rails which cause a web of power connections between them and no external connections to power poles :-(
too bad that i couldn't test any of these two points now - see my other post about a bug report when starting factorio :-(
