With the single cab, you can always stand it on end for a bit more height. Also makes it easier to use the handle if it's always facing upwards.

Jack connectors aren't really designed for reliable high power operation. They are only really any good for up to 100W. Above that and you're much better off with a good Speakon lead.

I'll have a look for a Loopi switch for my BH250. I must rebuild my bass cab though to something more like the size of the Hartke. My 2x10 Bill Fitzmaurice 'Jack' cab is loud, but about twice the size of your cab.

Really hope you're happy with the sound once you get it all together. It will certainly be loud enough for rehearsals!