I checked out the RCD site but it just says "info coming soon" on the TJ 4 inch lift. I have been doing a lot of research on lifts and after seeing what one of my friends did to his 2010 Rubicon JK, I decided to take the basic route for a while. I just have the 1.75 coil spacers, rancho shocks, and 265/75/16 Duratracs, which netted around 2.25" total lift compared to stock with 30x9.5s. I am satisfied, no vibrations or rubbing and my lowest point is now 10.5" off the ground. I had no noticable loss of power either (and mines a 4 banger!)
My friend with the JK rubicon used a 4.5" rubicon express long arm lift and is running 37s. It rides fine and is a monster off road, but so far he has had to lower his gears to 5.35, have the rear axle rotated (spring mounts relocated) to reduce the driveshaft angle, upgrade the rear driveshaft, and replace the automatic transmission. Needless to say he has put some bucks into it but then again he can go on level 5/6 trails.