Here is my take on the legs. A Gitzo Series 3 is likely your best choice based on your current and potential future equipment. Those legs currently cost $800 USD.
If you are looking to save a few $$$ an excellent alternative is a Feisol 3472 with RAL. That set of legs will cost $570 USD. The money you save on the legs will get 2/3 the way to the cost of the Q20.
Now, for the facts that back up the suggestion above. I have owned and extensively used the Feisol 3471, the older, non-ral version of the model mentioned above. It is a very good pod that served me well under all types of conditions, some very harsh like salt water and sand.
I own a Gitzo 3541LS and have tested the Feisol 3472. The test consisted of my D300, Jobu Pro Gimbal and my 500/4 AF-S lens. The test was a series of tap tests with the camera/lens mounted to both tripods. I found that the Feisol performed as well as the Gitzo. Field use confirmed what was seen in the tap tests.
The caveat here is that the Gitzo is a series 3 (32mm) and the Feisol is a Series 4 (37mm). The Feisol weighs about the same, folded it is about the same size and I would assume it is about the same bulk due to the new triangular top plate of the Gitzo 3542LS. The Feisol will easily handle your current and future equipment and will be an excellent choice for your lunar shots. You can review all the specs on the tripod here.
So in summary if you would like the performance and stability of the Gitzo 3542LS from an alternative manufacture that will save you $$$ you can put towards the Markins Q20 then you may want to consider the large Feisol.
Note: I am not sure how the cost of the Feisol vs Gitzo in Euros would compare. I will leave that to you to figure out.