I run all balanced with a 30' run between amp and preamp. My Prosaic speaker cables are under two meters. I have my turntable and phono preamp in another room, with the turntable suspended from the ceiling. The phono preamp is connected to the preamp with balanced cables.
If you search on Nelson Pass and cable impedance or damping he wrote a quasi-scientific paper on damping factor, transformer/capacitive coupled amps, resistance/damping including OTLs, I believe, cable/speaker interaction, speaker cable length and gauge, and resistance, inductance and capacitance. He measures the interaction of different types of cables with different types of speakers, dynamic and electrostatic. Roger Sanders has a discussion/paper too at his sanderssound web site.
The only reason you see ALL the equipment sitting between the speakers at hi-fi shows, pictures in magazines or at dealers' is because they want to keep your attention fixed on the equipment and fancy racks rather than a proper set up. The only saving grace is the short speaker cables runs, if they are the correct cables in terms of I, R, and Z. The monstrous cables with boxes on the end that sell for gigabucks merely have IRZ networks tailored to the particular speaker. One can do just as well at a much lower price if one follows basic electronics.
Oh, has anyone seen an audio company where their speaker cables are shunted to ground through the earth lead of an altered male mains plug. This should produce a positive effect at least according to electronic theory. Guess I should say neutered!