If you want to run a separate cabinet -- there are advantages to that -- you can put your Twin chassis into a head cabinet, like I used to do ...
The problem with putting JBL E-120s into a Twin is it makes it unbelievably heavy. I have yet to hear anything that sounds "exactly" like the E120s. The E120 is not that pleasing heard on its own, actually, but man, it cuts through the mix well.
The separate cab is nice because you can carry a 1X12 for smaller venues and the 2X12 for bigger ones (or the 3X12 if you're playing Madison Square Garden). It's also much easier to swap speakers in the 2X12 cabinets with the clips if you want something that breaks up a little sometimes.
I have the above head cab and light-duty road case for sale for $350 if anyone wants it; it's a custom job with cocoa tolex and a wheat grille, pre-drilled for the head and reverb tank. Like-new shape.
One thing you learn pretty quickly when you are gigging regularly ... casters are your friend. The road case above has little wheels so you can tilt it up and roll it. The 2X12 I used had a pro AVS road case with great casters on it, I could stack everything on it and roll it into the venues.
Stairs, you're on your own ... LOL