Well you can peice together any kit configuration you want it just takes time. I am running RE ZJ 3.5" springs, RE 3.5" leafs, RE 3/4" spacer, and RE boomerang shackles. This has netted me approximately 5" of lift. With an ARB up front and a 33" spare inside w/ spare axle assemblies, tools, hi-lift.
SO basically if you look at DPGs 5" hybrid they are subbing the RE 4.5" ZJ springs for RE 3.5" ZJ springs and the 4.5" leafs for 3.5" leafs. The 3.5" leafs will ride much better and flex much better IMO. Its all pretty much a guess and play around game.
The RE 5.5" kit is going to sit somewhere around 7" on most jeeps that are not running winch bumpers, winches, tire carriers, etc. The DPG kit will sit around 6" unless you have a similar weight configuration.
But I think you are misreading that the DPG kit is subbing 5.5" XJ springs for 3.5" XJ springs. It's subbing 4.5" ZJ springs for 3.5" ZJ springs.
If you want to see my setup check out
www.backyard4x4.com Mine is the Black XJ. Woodkrawler (white XJ) is running RE's 4.5" kit and his sits just a tad lower than mine...
EDIT: The DPG kit seems to be a little expensive for what you're gettig. The cheapest place I have been able to find RE parts is
www.dc4x4.com Ive ordered everything from him but you need to give him a call to get an accurate price quote.
I would just about say you could get into the RE6200 5.5" kit w/ drop brackets AND shocks AND possibly a RE hack & tap for less than what DPG is asking for the lift kit alone..... Call and let me know if im right or wrong..