I say the 20 is a good addition. It's perfect for some good extra light in most situations. I have the Rigid 20 e series mounted and its worth the money. I had another brand from a forum vendor and then upgraded to the rigid and it's night and day between the two. You get what you pay for.
If you're going to do night runs, you'll need more lights, if you're just running it for extra light in most situations, it's great.
I don't like running at night, but i have been caught at the end of a run when it's dark and the 20 along with some hood mounted lights helped light it up enough to see more then what the stock headlights would show. I have no intention of adding more lights, just going to change my hood mounted lights.
If you plan to run at night or just want to blow your *** on lights for your truck, go nuts, you can add lights everywhere.