The Turris does just fine. It's equivalent, mostly, to a mid-oughts desktop.
The flexibility of keeping the adblock processing self-contained, rather than processing this on another box and rigging an update mechanism, is appealing.
The 'huge" file is 6MB. That's not immense, but it taxes (overly constrained, IMO) typical SOH router resources.
The flexibility afforded, for pennies to a few dollars, of, say, > 1 GB storage and 500 MB RAM, is tremendous.
I'm not sure what Busybox's sort does, though on an earlier iteration on a mid-oughts Linksys WRT54g router running dd-wrt, sorting was infeasible. I hadn't tried the awk trick.
It did have a Busybox awk though, which proved useful.
Will the BusyBox version of sort use files when there isn't enough RAM, will you have a big enough read/write flash partition for that?