I'm just too lazy for manual disco's lol. If you can do it, then fabing up your own frame welded sliders is by far the way to go to save money! I'd look into getting a PR44 and having a ARB installed on your current axle. The mod of your current rear axle(shafts, re-gear, and locker), a PR44 with ARB, and he ARB air system to run it and you'd be up and running with better than Rubi (better gears, better lockers, better axle shafts) for around 9K. All combined, that's WAY less than the lose in trade in/re-sale value of your current rig plus cost of a new rig, plus taxes, plus title and registration costs, plus replaceing any mods you've already done on your current rig.
I think you can tell I'm super biased on the financial standpoint of sticking with your current rig and using all that saved money for better than Rubi axles and aftermarket parts.
EDIT: and I say this as I did the same thing with my old 07 Sahara when I upgraded to a 13 Rubi. I'd do it all over again because of the engine...but if it weren't for that, then no way would I have sold my old JK for a new one until the next model year came out at least.