@ejlif The problem you have is that you need to drive long cables. That means that all passive control systems are out. It also means single-ended preamps are out.
You need a balanced line preamp, and further, one that can drive long cables. You might think that 'because its balanced it can drive long cables' but its not as simple as that. To do that, there are a number of hurdles that the preamp must clear and most in high end audio do not. There is a standard for balanced line operation; most high end manufacturers either ignore it or worse, don't seem to be aware that it exists.
Its called 'AES48'.
If your preamp supports AES48, driving the long interconnects is a walk in the park, and the cost of the cable won't amount to anything with regards to the sound quality. So when you look at these suggestions and talk to manufacturers, ask if their preamp supports the standard. If they don't know about it, or don't know, that is telling you that they do not.
I think there are four preamps suggested so far that support the standard. They are the Dan Sachs preamp (when used with its output transformer to produce a balanced output), the Benchmark and the two Atma-Sphere preamps. There may be others- ask the manufacturer when investigating!