I disagree with Sattothestars. If you're not using balanced IC, it should be as short as possible. Otherwise, it will act like antenna - any noise it will pick up will be amplified together with the music. On the other hand, if you add some noise to already amplified music it will have smaller effect on the output signal. Just make sure that you long speaker cables are heavy enough not to lose any signal along the way and have insulation of good dielectric quality to minimize the stray capacitance.
Long IC/Short Speaker or Short IC/ Long Speaker
For monoblocks setup, would it it be better sonically to run long interconnects (from pre-amp to amp) and shorter speaker cables (from amp to speakers) or to run short interconnects and longer speaker cables? Does it make a difference? One thing I must note is that I can only run RCA connection IC. I do understand that the gain is more gain when using XLR IC. Thanks for your help.