Speaker cables

Hello Together After some research on the internet, the subject of speaker cables has totally confused me.... Here's the situation: I want to set up a new home cinema setup for a rather small room (approx. 25 sqm). Although I'm very sensitive to audio quality, I've only had rather poor and basic loudspeakers up to now, but this should change now. The first step will probably be to install Klipsch 5.1.2 surrounds and the second step 5.1.4 surrounds. They will be driven by a Marantz SR-6011 AV receiver, which delivers 9x 185 watts. 2 difficulties arise from the setup at the moment. 1. the loudspeaker(s) at the rear right will have a cable distance of 12.5 - 14m. The question is whether 2.5mm speaker cable is sufficient, or do I risk a loss of quality? Opinions are divided on the Internet. The second thing that is confusing for me is a wattage specification for copper cable (suitable for up to 120W per channel)... But I haven't found one that says up to 185 watts... Does that make a difference? Thank you very much for your help, the subject of speaker cables seems very confusing to me, and if I am already commissioning a new system, I would like to do it as well as possible. I am looking forward to your feedback.