Speaker Cables

Great all around cables period Wireworld Eclipse  they checks
all the boxes silver copper connectors ,not brass like most, 6-9s pure copper isolated conductors, and lowest dielectric insulation 
at a decent price Galen carol audio ,I got great deals ad service on them.

I like the single-crystal 5-nines silver ones. About $1,500 on Amazon for for 3-meter pairs. Or, make your own from 18 AWG fine silver wire and 1.5 mm PTFE tubing. 

I would use a set of kimber tc cables with tc custom jumbers a lot of sound for not a lot of money.

it is of course system dependent as well as dependent on listener tastes, but having said that proacs (and d30r's specifically, which i have) tend to highlight the treble and lean out the midbass a bit, so best to use all copper cables that provide some warmth... no silver/silver plating...

tuneful cables of brooklyn makes very affordable cables using belden 9497 copper with excellent terminations... it would be a very cost effective very good sounding place to start... not to say others won't work well

Speaker cables make a difference. And I have had success with Canare 4s11 internal biwire - I preferred them to audioquest rocket 44. 
I encourage testing because I thought it was ‘a myth’ until I tried it.