.. that you've got a nice problem to have!! Whatever you decide out of these 3 in the end you'll have a great sample from the elite.
Those 3 watches are very different watches so it really depend on what you like. Which metals are you thinking of?
With RL, the look is understated classic. The roman numerals dial make it the best dress watch out of the 3. Langes are VERY solid and feel substantial on the hand or wrist. Craftsmenship is really the best you can get and the finishing is jaw dropping. Need to say no more about "german engineering".
CS, in my opinion are amazingly accurate. The dial design is very unique and "signature" Journe. The CS being it's iconic piece. It'll be thinner and not feel as substantial than the RL though. The rose gold movement is a nice sight to behold.
The 5130 is the most complicated out of these 3, and Patek is afterall Patek. Finishing will also be top notch and easily the most recognisable brand out of the 3.
At the end of the day it really depend on what you want as your second watch after a Master Perpetual. If you want more complications, the 5130 fits the bill. If you want a simpler watch to go with the already complicated Master Perpetual, then RL or CS. Another important factor is whether you want everybody to know your watch or you're the kind of person that like to appreciate it secretly (I'm the latter type). With the 5130, everyone will see a Patek Philippe, but not everyone (apart from us here!) would know about Lange and Journe.
Finally as we always say, the most deciding factor is how you feel about it on your wrist. You'll have to try it all on and see which one sings to you the most! For this amount of money you would want to get the biggest enjoyment out of it! At the moment you sound like you perfer the aesthetic of CS over the other 2 so I assume you have tried them on already. If Journe speaks to your the most, I can't think of a reason for not going for that.
Good luck with your choice and please let us know how it goes!