If you add the springs you should get a little bit of lift on the front for a more leveled look. You can add some spacers for the same. The Rubi Shocks are an improvement over stock though for sure either way.
This is an old thread, but I can tell you first hand that the Rubicon Fox shocks on stock overland springs is a pretty nice set up. It still rides great, but it controls the ride a lot better and eliminates the bounciness from the rear when you go over bumps. Overall, it feels a lot more solid and less floaty. I have a full rubicon take off suspension, and eventually, I'll probably put the Rubicon springs on it, but its a huge improvement for now. I don't need any lift on mine, I only have 33.5" A/Ts on mine. I'll probably just do it because I can and have the parts and 3/4-1" higher wouldn't be a bad thing.
Those shocks are super stiff and very hard to compress by hand, I'd highly recommend jacking your Jeep up and putting jack stands under the frame so the suspension will droop. I should have done that from the beginning. The back two kicked my butt doing it with the Jeep on the ground. The front was way easier to do when I did it the correct way.